Overview
This review chapter reinforces the concepts you have already learned related to the OSI reference model, LANs and IP addressing. Understanding these complex topics is the first step toward understanding the Cisco Internetwork Operating System (IOS), which is a major topic in this curriculum. You need to have a firm grasp of the internetworking principles surveyed in this chapter before attempting to understand the complexities of the Cisco IOS.

 

Content
1.1 The OSI Model
1.1.1 Layered network model
New business practices are driving changes in enterprise networks. Employees at corporate headquarters and in worldwide field offices, as well as telecommuters in home offices, need immediate access to data, regardless of whether the data is on centralized or departmental servers. Enterprises such as corporations, agencies, schools, or other organizations that tie together their data communication, computing, and file servers need:
  • interconnected LANs that provide access to computers or file servers in other locations
  • higher bandwidth onto the LANs to satisfy the needs of the end users
  • support technologies that can be relayed for WAN service

To improve communication with partners, employees, and customers, enterprises are implementing new applications such as electronic commerce, videoconferencing, voice over IP, and distance learning. Businesses are merging their voice, video, and data networks into global enterprise networks as shown in Figure  that are critical to the organization's business success.

Enterprise networks are designed and built to support current and future applications. To accommodate increasing requirements for bandwidth, scalability, and reliability, vendors and standards bodies introduce new protocols and technologies at a rapid rate. Network designers are challenged to develop state-of-the-art networks even though what is considered state-of-the-art changes on a monthly, if not weekly basis.

By dividing and organizing the networking tasks into separate layers/functions, new applications can be handled without problems. The OSI reference model organizes network functions into seven categories, called layers. Data flows from upper-level user applications to lower-level bits that are then transmitted through network media. The task of most wide area network managers is to configure the three lowest layers. Peer-to-peer functions use encapsulation and de-encapsulation as the interface for the layers.

As shown in the Figure there are seven layers in the OSI reference model, each of which has separate distinct functions. The Transmission Control Protocol/Internet Protocol (TCP/IP) models' functions fit into five layers. This separation of networking functions is called layering. Regardless of the number of layers, however, the reasons for the division of network functions include the following:

  • to divide the interrelated aspects of network operations into less complex elements
  • to define standard interfaces for plug-and-play compatibility and multivendor integration
  • to enable engineers to focus their design and development efforts on a particular layer's functions
  • to promote symmetry of the different internetwork modular functions for the purpose of interoperability
  • to prevent changes in one area from significantly affecting other areas, so that each area can evolve more quickly
  • to divide the complex operations of internetworking into discrete, more easily learned operational subsets

 

Content
1.1 The OSI Model
1.1.2 The OSI model layer functions
Each layer of the seven-layer OSI reference model serves a specific function. The functions are defined by the OSI and can be used by any network products vendor. -

The layers are:

  • Application -- The application layer provides network services to user applications. For example, a word processing application is serviced by file transfer services at this layer.
  • Presentation -- This layer provides data representation and code formatting. It ensures that the data that arrives from the network can be used by the application, and it ensures that the information sent by the application can be transmitted on the network.
  • Session -- This layer establishes, maintains, and manages sessions between applications.
  • Transport -- This layer segments and reassembles data into a data stream. TCP is one of the transport layer protocols used with IP.
  • Network -- This layer determines the best way to move data from one place to another. Routers operate at this layer. You will find the IP (Internet Protocol) addressing scheme at this layer.
  • Data Link -- This layer prepares a datagram (or packet) for physical transmission across the medium. It handles error notification, network topology, and flow control. This layer uses Media Access Control (MAC) addresses.
  • Physical -- This layer provides the electrical, mechanical, procedural, and functional means for activating and maintaining the physical link between systems. This layer uses physical media such as twisted-pair, coaxial, and fiber-optic cable.

 

Content
1.1 The OSI Model
1.1.3 Peer-to-peer communications
Each layer uses its own layer protocol to communicate with its peer layer in another system. Each layer's protocol exchanges information, called protocol data units (PDUs), with its peer layers. A layer can use a more specific name for its PDU. For example, in TCP/IP the transport layer of TCP communicates with the peer TCP function by using segments. Each layer uses the services of the layer below it in order to communicate with its peer layer. The lower layer service uses upper layer information as part of the PDUs that it exchanges with its peer.

The TCP segments become part of the network layer packets (datagrams) that are exchanged between IP peers. In turn, the IP packets become part of the data link frames that are exchanged between directly-connected devices. Ultimately, these frames become bits, as the data is finally transmitted by the hardware that is used by the physical layer protocol.

Each layer depends on the services of the OSI reference model layer that is below it. In order to provide this service, the lower layer uses encapsulation to put the protocol data unit (PDU) from the upper layer into its data field, then it can add whatever headers and trailers the layer wishes to use to perform its function.

As an example, the network layer provides a service to the transport layer, and the transport layer presents data to the internetwork subsystem. The network layer has the task of moving that data through the internetwork. It accomplishes this task by encapsulating the data within a packet.

This packet includes a header containing information that is necessary to complete the transfer, such as source and destination logical addresses.

The data link layer in turn provides a service to the network layer. It encapsulates the network layer packet in a frame. The frame header contains information that is necessary to complete the data link functions (e.g. physical addresses). And finally, the physical layer provides a service to the data link layer: It encodes the data link frame into a pattern of 1s and 0s for transmission through the medium (usually a wire). -

  

Content
1.1 The OSI Model
1.1.4 Five steps of data encapsulation
As networks perform services for users, the flow and packaging of the user's original information go through several changes. In this example of internetworking, there are five conversion steps.

Step 1
A computer converts an e-mail message into alphanumeric characters that can be used by the internetworking system. This is the data.

Step 2
The message data is then segmented for transport on the internetwork system by the transport layer. The transport layer ensures that the message hosts at both ends of the e-mail system can reliably communicate.

Step 3
The data is then converted to a packet, or datagram, by the network layer. The packet also contains a network header that includes a source and destination logical address. The address helps network devices send the packet across the network along a chosen path.

Step 4
Each data-link layer device puts the packet into a frame. The frame enables the device to connect to the next directly-connected network device on the link.

Step 5
The frame is changed to a pattern of 1s and 0s for transmission on the medium (usually a wire). A clocking function enables the devices to distinguish bits as they travel across the medium.
The medium on the physical internetwork can vary along the path. For example, an e-mail message may originate on a LAN, cross a campus backbone, and continue through a WAN link until it reaches its destination on another remote LAN.

 

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1.2 LANs
1.2.1 LAN devices and technologies

The major characteristics of LANs are as follows:

  • The network operates within a building or floor of a building.
  • LANs provide multiple connected desktop devices (usually PCs) with access to high-bandwidth media.
  • By definition, the LAN connects computers and services to a common Layer 1 medium. LAN devices include:
  • Bridges that connect LAN segments and help filter traffic
  • Hubs that concentrate LAN connections and allow use of twisted-pair copper media
  • Ethernet switches that offer full-duplex, dedicated bandwidth to segments or desktop traffic
  • Routers that offer many services, including internetworking and broadcast control traffic
The following three LAN technologies (shown in the graphic) account for virtually all deployed LANs:
  • Ethernet -- The first of the major LAN technologies, it runs the largest number of LANs.
  • Token-Ring -- From IBM, it followed Ethernet and is now widely used in a large number of IBM networks.
  • FDDI -- Also uses tokens, and is now a popular campus LAN.
On a LAN, the physical layer provides access to the network media. The data link layer provides support for communication over several types of data links, such as Ethernet/IEEE 802.3 media. You will be studying the Ethernet IEEE 802.3 LAN standards. Figure shows the most common Layer 1 media used in networking today - coaxial, fiber-optic, and twisted-pair cable.  Addressing schemes such as Media Access Control (MAC) and Internet Protocol (IP) provide a very structured method for finding and delivering data to computers or to other hosts on a network.

 

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  1.2 LANs
1.2.2 Ethernet and IEEE 802.3 standards
The Ethernet and IEEE 802.3 standards define a bus topology LAN that operates at a baseband signaling rate of 10 Mbps. Figure illustrates the three defined wiring standards:
  • 10BASE2 (thin Ethernet) -- allows coaxial cable network segments up to 185 m. long
  • 10BASE5 (thick Ethernet) -- allows coaxial cable network segments up to 500 m. long
  • 10BASE-T -- carries Ethernet frames on inexpensive twisted-pair wiring

The 10BASE5 and 10BASE2 standards provide access for several stations to the same LAN segment. Stations are attached to the segment by a cable that runs from an attachment unit interface (AUI) in the station to a transceiver that is directly attached to the Ethernet coaxial cable.

Because 10BASE-T provides access for a single station only, stations that are attached to an Ethernet LAN by 10BASE-T are almost always connected to a hub or a LAN switch. In this arrangement, the hub or LAN switch is the same as an Ethernet segment.

The Ethernet and 802.3 data links prepare data for transport across the physical link that joins two devices.  For example, as Figure shows, three devices can be directly attached to each other over the Ethernet LAN. The Macintosh on the left and the Intel-based PC in the middle show MAC addresses used by the data link layer. The router on the right also uses MAC addresses for each of the LAN side interfaces. The Ethernet/802.3 interface on the router uses the Cisco IOS interface type abbreviation "E" followed by an interface number (e.g. "0", as shown in Figure ).

Broadcasting is a powerful tool that can send a single frame to many stations at the same time.  Broadcasting uses a data link destination address of all 1s (FFFF.FFFF.FFFF in hexadecimal). As Figure shows, if station A transmits a frame with a destination address of all 1s, stations B, C, and D will all receive and pass the frame to their upper layers for further processing.

When improperly used, broadcasting can seriously affect the performance of stations by unnecessarily interrupting them. Broadcasts should, therefore, be used only when the MAC address of the destination is unknown, or when the destination is all stations.

 

Content
1.2 LANs
1.2.3 Carrier sense multiple access with collision detection
On an Ethernet LAN, only one transmission is allowed at any given time. An Ethernet LAN is referred to as a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) network. This means that one node's transmission traverses the entire network and is received and examined by every node. When the signal reaches the end of a segment, terminators absorb it to prevent it from going back onto the segment.

When a station wishes to transmit a signal, it checks the network to determine whether another station is currently transmitting. If the network is not being used, the station proceeds with the transmission. While sending a signal, the station monitors the network to ensure that no other station is transmitting at that time. It is possible that two stations could both determine that the network is available and start transmitting at approximately the same time. If this should occur, they would cause a collision, as is illustrated in the upper part of the graphic.

When a transmitting node recognizes a collision, it transmits a jam signal that causes the collision to last long enough for all other nodes to recognize it. All transmitting nodes would then stop sending frames for a randomly selected period of time before attempting to retransmit. If subsequent attempts also result in collisions, the node would try to retransmit as many as fifteen times before finally giving up. The clocks indicate various backoff timers. If the two timers are sufficiently different, one station would succeed the next time.

 

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1.2 LANs
1.2.4 Logical (IP) addressing
An essential component of any network system is the process that enables information to locate specific computers systems on a network. Various addressing schemes are used for this purpose, depending on the protocol family being used. For example, AppleTalk addressing is different from TCP/IP addressing, which in turn is different from IPX addressing.

Two important types of addresses are data link layer addresses and network layer addresses. Data link layer addresses, also called physical hardware addresses or MAC addresses , are typically unique for each network connection. In fact, for most LANs, data link layer addresses are located on the NIC (network interface card). Because a typical computer system has one physical network connection, it has only a single data link layer address. Routers and other systems that are connected to multiple physical networks can have multiple data link layer addresses. As their name implies, data link layer addresses exist at Layer 2 of the OSI reference model.

Network layer addresses (also called logical addresses or IP addresses for the Internet Protocol suite) exist at Layer 3 of the OSI reference model. Unlike data link layer addresses, which usually exist within a flat address space, network layer addresses are usually hierarchical. In other words, they are like postal addresses that describe a person's location by indicating a country, state, ZIP Code, city, street, house address, and name. One example of a flat address is a U.S. Social Security number. Each person has a unique Social Security number, people can move around the country and obtain new logical addresses depending on their city, street, or ZIP Code, but their Social Security numbers remain unchanged.

 

Content
1.2 LANs
1.2.5 MAC addressing
In order for multiple stations to share the same media and still identify each other, the MAC sublayers define hardware or data link addresses called the MAC addresses. Each LAN interface has a unique MAC address. In most NICs, the MAC address is burned into ROM. When the NIC initializes, this address is copied into RAM.

Before directly connected devices on the same LAN can exchange a data frame, the sending device must have the destination device's MAC address. One way in which the sender can ascertain the MAC address that it needs is to use an ARP (Address Resolution Protocol). The graphic illustrates two ways in which a TCP/IP example, ARP, is used to discover a MAC address.

In the first example, Host Y and Host Z are on the same LAN. Host Y broadcasts an ARP request to the LAN looking for Host Z. Because Host Y has sent out a broadcast, all devices including Host Z will look at the request; however, only Host Z will respond with its MAC address. Host Y receives Host Z's reply and saves the MAC address in local memory, often called an ARP cache. The next time Host Y needs to directly communicate with Host Z, it uses the stored MAC address.

In the second example, Host Y and Host Z are on different LANs, but can access each other through Router A. When Host Y broadcasts its ARP request, Router A determines that Host Z cannot recognize the request because Router A detects that the IP address for Host Z is for a different LAN. Because Router A also determines that any packets for Host Z must be relayed, Router A provides its own MAC address as a proxy reply to the ARP request. Host Y receives Router A's response and saves the MAC address in its ARP cache memory. The next time Host Y needs to communicate with Host Z, it uses the stored MAC address of Router A.

 

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1.3 TCP/IP Addressing
1.3.1 TCP/IP environment
In a TCP/IP environment, end stations communicate with servers or other end stations. This can occur because each node using the TCP/IP protocol suite has a unique 32 bit logical address. This address is known as the IP address. Each company or organization connected to an internetwork is perceived as a single unique network that must be reached before an individual host within that company can be contacted. Each company network has an address; the hosts that live on that network share that same network address, but each host is identified by the unique host address on the network.

Content
1.3 TCP/IP Addressing
1.3.2 Subnetworks
Subnets improve the efficiency of network addressing. Adding subnets does not change how the outside world sees the network, but within the organization, there is additional structure. In Figure , the network 172.16.0.0 is subdivided into four subnets: 172.16.1.0, 172.16.2.0, 172.16.3.0, and 172.16.4.0. Routers determine the destination network by using the subnet address, which limits the amount of traffic on the other network segments.

From an addressing standpoint, subnets are an extension of a network number. Network administrators determine the size of subnets based on the expansion needs of their organizations. Network devices use subnet masks to identify which part of the address is for the network and which part represents host addressing.

Example of Class C subnetting.

In Figure , the network has been assigned the Class C address 201.222.5.0. Assuming that 20 subnets are needed, with a maximum of 5 hosts per subnet, you need to subdivide the last octet into a subnet and a host, and then determine what the subnet mask will be. You need to select a subnet field size that yields enough subnetworks. In this example, selecting 5-bits gives you 20 subnets.

In the example, the subnet addresses are all multiples of 8 - 201.222.5.16; 201.222.5.32; and 201.222.5.48. The remaining bits in the last octet are reserved for the host field. The 3 bits in the example are enough for the required five hosts per subnet (actually, giving you host numbers 1 - 6). The final host addresses are a combination of the network/subnet segment's starting address plus each host's value. The hosts on the 201.222.5.16 subnet would be addressed as 201.222.5.17, 201.222.5.18, 201.222.5.19, and so forth.

A host number of 0 is reserved for the wire (or subnet) address, and a host value of all 1s is reserved because it selects all hosts-that is, it is a broadcast. A table used for the subnet planning example is on the following page. Also, a routing sample shows the combining of an arriving IP address with a subnet mask to derive the subnet address (also called the subnet number). The extracted subnet address should be typical of the subnets generated during this planning exercise.

Example of Class B subnetwork planning

In Figure , a Class B network is subnetted to provide up to 254 subnets and 254 useable host addresses. 

Example of Class C subnetwork planning

In Figure , a Class C network is subnetted to provide 6 host addresses and 30 useable subnets.

 

Content
1.4
Host Layers (the Upper 4 Layers of the OSI Model)
1.4.1 Application, presentation, and session layers

Application Layer  

In the context of the OSI reference model, the application layer (Layer 7) supports the communicating component of an application. It does not provide services to any other OSI layer. However, it does provide services to application processes lying outside the scope of the OSI model (e.g. spreadsheet programs, Telnet, WWW, etc.) A computer application can function completely by using only the information that resides on its computer. However, an application might also have a communicating component that can connect with one or more network applications. Several types are listed in the right column of the Figure .

An example of such an application might include a word processor that can incorporate a file transfer component that allows a document to be transferred electronically across a network. The file transfer component qualifies the word processor as an application in the OSI context, and therefore, belongs in Layer 7 of the OSI reference model. Another example of computer application that has data transfer components is a Web browser such as Netscape Navigator and Internet Explorer. Whenever you visit a Web site, the pages are transferred to your computer.

Presentation Layer

The presentation layer (Layer 6) of the OSI reference model is responsible for presenting data in a form that a receiving device can understand. It serves as the translator - sometimes between different formats - for devices that need to communicate over a network, by providing code formatting and conversion. The presentation layer (Layer 6) formats and converts network application data into text, graphics, video, audio, or whatever format is necessary for the receiving device to understand it.

The presentation layer is not only concerned with the format and representation of data, but also with the data structure that the programs use. Layer 6 organizes the data for Layer 7.
To understand how this works, imagine that you have two systems. One system uses EBCDIC, and the other uses ASCII to represent data. When the two systems need to communicate, Layer 6 converts and translates the two different formats.

Another function of Layer 6 is the encryption of data. Encryption is used when there is a need to protect transmitted information from unauthorized receivers. To accomplish this task, processes and codes located in Layer 6 must convert the data. Other routines located in the presentation layer compress text and convert graphic images into bit streams so that they can be transmitted across a network.

Layer 6 standards also guide how graphic images are presented. Following are some examples:

  • PICT -- a picture format used to transfer QuickDraw graphics between Macintosh or PowerPC programs
  • TIFF -- tagged image file format, used for high-resolution, bit-mapped images
  • JPEG -- from the Joint Photographic Experts Group, used for photographic quality images

Other Layer 6 standards guide the presentation of sound and movies. Included in these standards are the following:

  • MIDI -- musical instrument digital interface for digitized music
  • MPEG -- the motion picture experts group's standard for the compression and coding of motion video for CDs, digital storage, and bit rates up to 1.5 Mbps
  • QuickTime -- a standard that handles audio and video for Macintosh and PowerPC programs

Session Layer

The session layer (Layer 5) establishes, manages, and terminates sessions between applications. It coordinates the service requests and responses that occur when applications establish communications between different hosts.

 

Content
1.4
Host Layers (the Upper 4 Layers of the OSI Model)
1.4.2 Transport Layer

The transport layer (Layer 4) is responsible for transporting and regulating the flow of information from source to destination reliably and accurately. Its functions include:

  • connection synchronization
  • flow control
  • error recovery
  • reliability through windowing
The transport layer (Layer 4) enables a user's device to segment several upper-layer applications for placement on the same Layer 4 data stream, and enables a receiving device to reassemble the upper-layer application segments. The Layer 4 data stream is a logical connection between the endpoints of a network, and provides transport services from a host to a destination. This service is sometimes referred to as end-to-end service.
As the transport layer sends its data segments, it also ensures the integrity of the data. This transport is a connection-oriented relationship between communicating end systems. Some of the reasons for accomplishing reliable transport are as follows:
  • It ensures that senders receive acknowledgement of delivered segments.
  • It provides for retransmission of any segments that are not acknowledged.
  • It puts segments back into their correct sequence at the destination device.
  • It provides congestion avoidance and control.
One of the problems that can occur during data transport is overflowing buffers on receiving devices. Overflows can present serious problems that result in data loss. The transport layer uses a method called flow control to solve this problem.

 

Content
1.4
Host Layers (the Upper 4 Layers of the OSI Model)
1.4.3 Transport layer functions
Each of the upper-level layers performs its own functions. However, their functions depend on lower-layer services. All four upper layers - application (Layer 7), presentation (Layer 6), session (Layer 5), and transport (Layer 4) - can encapsulate data in end-to-end segments.

The transport layer assumes that it can use the network as a cloud to send data packets from source to destination. If you examine the operations that take place inside the cloud, you can see that one of the functions involves selecting the best paths for a given route. You begin to see the role that routers perform in this process.

Segmentation of upper-layer applications

One reason for using a multi-layer model such as the OSI reference model is that multiple applications can share the same transport connection. Transport functionality is accomplished segment by segment. This means that different data segments from different applications, being sent to the same destination or to many destinations, are sent on a first-come, first-served basis.

To understand how this works, imagine that you are sending an e-mail and transferring a file (FTP) to another device on a network. When you send your e-mail message, before the actual transmission begins, software in your device sets the SMTP (e-mail) port number and the originating program port number. As each application sends a data stream segment, it uses the previously defined port number. When the destination device receives the data stream, it separates and sorts the segments so that the transport layer can pass the data up to the correct corresponding destination application.

TCP establishes a connection

In order for data transfer to begin, one user of the transport layer must establish a connection-oriented session with its peer system. Then, both the sending and receiving application programs must inform their respective operating systems that a connection will be initiated. In concept, one device places a call to another device that the other device must accept. Protocol software modules in the two operating systems communicate by sending messages across the network to verify that the transfer is authorized and that both sides are ready. After all synchronization has occurred, a connection is established, and data transfer begins. During transfer, the two devices continue to communicate with their protocol software to verify that they are receiving the data correctly.

The graphic depicts a typical connection between sending and receiving systems. The first handshake requests synchronization. The second and third handshakes acknowledge the initial synchronization request, and synchronize the connection parameters in the opposite direction. The final handshake segment sends an acknowledgement to the destination that both sides agree that a connection has been established. As soon as the connection has been established, data transfer begins.

TCP sends data with flow control

While data transfer is in progress, congestion can occur for two different reasons. First, a high-speed computer might generate traffic faster than a network can transfer it. Second, if many computers send datagrams simultaneously to a single destination, that destination can experience congestion. When datagrams arrive too quickly for a host or gateway to process, they are temporarily stored in memory. If the traffic continues, the host or gateway eventually exhausts its memory and discards any additional datagrams that arrive.

Instead of allowing data to be lost, the transport function can issue a "not ready" indicator to the sender. This indicator acts like a stop sign and signals the sender to stop sending data. When the receiver is able to accept additional data, it sends a "ready" transport indicator, which is like a go signal. When the sending device receives this indicator, it resumes segment transmission.

TCP achieves reliability with windowing

Reliable connection-oriented data transfer means that data packets arrive in the same order in which they are sent. Protocols fail if any data packets are lost, damaged, duplicated, or received in the wrong order. In order to ensure transfer reliability, receiving devices must acknowledge receipt of each and every data segment.

If a sending device must wait for acknowledgement after sending each segment, it is easy to see that throughput could be quite low. However, because there is a period of unused time available after each data packet transmission and before processing any received acknowledgment, the interval can be used for transmitting more data. The number of data packets a sender is allowed to transmit without having received an acknowledgment is known as a window.

Windowing is an agreement between sender and receiver. It is a method of controlling the amount of information that can be transferred end-to-end. Some protocols measure information in terms of the number of packets; TCP/IP measures information in terms of the number of bytes. The examples in the Figure show the workstations of a sender and a receiver. One has a window size of 1, and the other a window size of 3. With a window size of 1, a sender must wait for an acknowledgment for every data packet transmitted. With a window size of 3, a sender can transmit three data packets before expecting an acknowledgment.

TCP acknowledgment technique

Reliable delivery guarantees that a stream of data that is sent from one device will be delivered through a data link to another device without duplication or data loss. Positive acknowledgment with retransmission is one process that guarantees reliable delivery of data streams. It requires a recipient to send an acknowledgment message to the sender whenever it receives data. The sender keeps a record of each data packet that it sends and then waits for the acknowledgment before sending the next data packet. The sender also starts a timer whenever it sends a segment, and retransmits the segment if the timer expires before the acknowledgment arrives.

Figure shows a sender transmitting Data Packets 1, 2, and 3. The receiver acknowledges receipt of the packets by requesting Packet 4. The sender, upon receiving the acknowledgment, sends Packets 4, 5, and 6. If Packet 5 does not arrive at the destination, the receiver acknowledges with a request to re-send Packet 5. The sender re-sends Packet 5 and waits for acknowledgment before transmitting Packet 7. -

 

Content
  Summary
Now that you have completed chapter one, you should have an understanding of the following:
  • The OSI model layer functions
  • Peer-to-peer communications
  • Five steps of data encapsulation
  • LAN devices and technologies
  • Ethernet and IEEE 802.3 standards
  • Carrier sense multiple access with collision detection
  • Logical (IP) addressing
  • MAC addressing
  • TCP/IP Addressing
  • Subnetworks
  • Application, presentation and session layers
  • Transport layer functions

 

Content
Overview
In "TCP/IP," you learned about Transmission Control Protocol/Internet Protocol (TCP/IP) and its operation to ensure communication across any set of interconnected networks. In this chapter, you will learn the details of IP address classes, network and node addresses, and subnet masking. In addition, you will learn the concepts you need to understand before configuring an IP address.

 

Content
10.1 IP Addressing and Subnetting
10.1.1 The purpose of IP address
In a TCP/IP environment, end stations communicate with servers or other end stations. This can occur because each node using the TCP/IP protocol suite has a unique 32-bit logical address. This address is known as the IP address and is specified in 32-bit dotted-decimal format. Router interfaces must be configured with an IP address if IP is to be routed to or from the interface. ping and trace commands can be used to verify IP address configuration.

Each company or organization listed on the Internet is seen as a single unique network that must be reached before an individual host within that company can be contacted. Each company network has an address; the hosts that live on that network share that same network address, but each host is identified by the unique host address on the network.


Content
10.1 IP Addressing and Subnetting
10.1.2 The role of host network on a routed network
In this section, you will learn basic concepts you need to understand before configuring an IP address. By examining various network requirements, you can select the correct class of address and define how to establish IP subnets. Each device or interface must have a host number that does not have all 0s in the host field. A host address of all 1s is reserved for an IP broadcast into that network. A host value of 0 means "this network" or "the wire itself" (e.g. 172.16.0.0). A value of 0 is also used, though rarely, for IP broadcasts in some early TCP/IP implementations. The routing table contains entries for network or wire addresses; it usually contains no information about hosts.

An IP address and a subnet mask on an interface achieve three purposes:

  • They enable the system to process the receipt and transmission of packets.
  • They specify the device's local address.
  • They specify a range of addresses that share the cable with the device.
Content
10.1 IP Addressing and Subnetting
10.1.3 The role of broadcast addresses on a routed network
Broadcasting is supported by IP. The messages are intended to be seen by every host on a network. The broadcast address is formed by using all 1s within a portion of the IP address.

Cisco IOS software supports two kinds of broadcasts - directed broadcasts and flooded broadcasts. Broadcasts directed into a specific network/subnet are allowed and are forwarded by the router. These directed broadcasts contain all 1s in the host portion of the address. Flooded broadcasts (255.255.255.255) are not propagated, but are considered local broadcasts. -

 

Content
10.1 IP Addressing and Subnetting
10.1.4
The assignment of router interface and network IP addresses
The Figure shows a small network with assigned interface addresses, subnet masks, and resulting subnet numbers. The number of routing bits (network and subnet bits) in each subnet mask can also be indicated by the "/n " format. 

Example: 
/8 = 255.0.0.0 
/24 = 255.255.255.0

Lab Activity
  In this lab you will work with other group members to design a 5-router network topology and an IP addressing scheme.

 

Content
10.2 The Role of DNS in Router Configurations
10.2.1 The ip addresses command
Use the ip address command to establish the logical network address of an interface. -

Use the
term ip netmask-format command to specify the format of network masks for the current session. Format options are:
  • bit count
  • dotted-decimal (default)
  • hexadecimal
Content
10.2
The Role of DNS in Router Configurations
10.2.2 The ip host command
The ip host command makes a static name-to-address entry in the router's configuration file.

 

Content
10.2 The Role of DNS in Router Configurations
10.2.3 Describe the ip name-server command
The ip name-server command defines which hosts can provide the name service. You can specify a maximum of six IP addresses as name servers in a single command. 

To map domain names to IP addresses, you must identify the host names, specify a name server, and enable DNS. Any time the operating system software receives a host name it does not recognize, it refers to DNS for the IP address of that device.

Content
10.2 The Role of DNS in Router Configurations
10.2.4 How to enable and disable DNS on a router
Each unique IP address can have a host name associated with it. The Cisco IOS software maintains a cache of host name-to-address mappings for use by EXEC commands. This cache speeds the process of converting names to addresses.

IP defines a naming scheme that allows a device to be identified by its location in IP. A name such as ftp.cisco.com identifies the domain of the File Transfer Protocol (FTP) for Cisco. To keep track of domain names, IP identifies a name server that manages the name cache. DNS (Domain Name Service) is enabled by default with a server address of 255.255.255.255, which is a local broadcast. The router(config)# no ip domain-lookup command turns off name-to-address translation in the router. This means that the router will not generate or forward name system broadcast packets.

 

Content
10.2
The Role of DNS in Router Configurations
10.2.5 Show hosts command
The show hosts command is used to display a cached list of host names and addresses.

 
Content
10.3 Verifying Address Configuration
10.3.1 Verification commands
 Addressing problems are the most common problems that occur on IP networks. It is important to verify your address configuration before continuing with further configuration steps.

 Three commands allow you to verify address configuration in your internetwork:                 
  • telnet -- verifies the application layer software between source and destination stations; is the most complete testing mechanism available
  • ping -- uses the ICMP protocol to verify the hardware connection and the logical address at the internet layer; is a very basic testing mechanism
  • trace -- uses TTL values to generate messages from each router used along the path; is very powerful in its ability to locate failures in the path from the source to the destination
Content
10.3 Verifying Address Configuration
10.3.2 The telnet and ping commands
The telnet command is a simple command that you use to see whether you can connect to the router. If you cannot telnet to the router but you can ping the router, you know the problem lies in the upper-layer functionality at the router. At this point, you may want to reboot the router and telnet to it again. 

The ping command sends ICMP echo packets and is supported in both user and privileged EXEC modes. In this example, one ping timed out, as reported by the dot (.) and four were successfully received, as shown by the exclamation point (!). These are the results that may be returned by the ping test:

Character

Definition

!

successful receipt of an echo reply

.

timed out waiting for datagram reply

U

destination unreachable error

C

congestion-experienced packet

I

ping interrupted (e.g. Ctrl-Shift-6 X)

?

packet type unknown

&

packet TTL exceeded

The extended ping command is supported only from privileged EXEC mode.  You can use the extended command mode of the ping command to specify the supported Internet header options. To enter the extended mode, enter ping <return>, then Y at the extended commands prompt.

 

Content
10.3 Verifying Address Configuration
10.3.3 The trace command
When you use the trace command as shown in the figure (output), host names are shown if the addresses are translated dynamically or via static host table entries. The times listed represent the time required for each of three probes to return.

NOTE: trace is supported by IP, CLNS, VINES, and AppleTalk.

When the trace reaches the target destination, an asterisk (*) is reported at the display. This is normally caused by a time out in response to one of the probe packets.

Other responses include:

!H -- The probe was received by the router, but not forwarded, usually due to an access list.
P -- The protocol was unreachable.
N -- The network was unreachable.
U -- The port was unreachable.
* -- Time out.

 

Content
10.4
Assigning New Subnet Numbers to the Topology
10.4.1 Topology challenge lab
Lab Activity
  You and your group members have just received your Cisco certification. Your first job is to work with other group members in designing a topology and IP addressing scheme. It will be a 5-router topology similar to the standard 5-router lab diagram as shown but with a few changes. Refer to the modified 5-router lab diagram shown in the worksheet. You must come up with a proper IP addressing scheme using multiple Class C addresses which are different from those of the standard lab setup. You will then use ConfigMaker to do your own diagram of the network. You may do this lab using the worksheets or work with the actual lab equipment if it is available.
Content
  Summary
  • In a TCP/IP environment, end stations communicate with servers or other end stations. This occurs because each node using the TCP/IP protocol suite has a unique 32-bit logical address known as the IP address.
  • An IP address with a subnet address on an interface achieves three purposes:
  • It enables the system to process the receipt and transmission of packets.
  • It specifies the device's local address.
  • It specifies a range of addresses that share the cable with the device.
  • Broadcast messages are those you want every host on the network to see.
  • You use the ip address command to establish the logical network address of this interface.
  • The ip host command makes a static name-to-address entry in the router's configuration file.
  • The ip name-server command defines which hosts can provide the name service.
  • The show hosts command is used to display a cached list of host names and addresses.
  • telnet, ping, and trace commands can be used to verify IP address configuration.

 

Content

 

Lab 10.1.4 IP addressing & subnets 

Estimated time: 30 min.

Objectives:

This Lab will focus on your ability to accomplish the following tasks:

  •  Design and implement a 5-router network topology 
  •  Develop an IP addressing scheme based on the topology
  •  Use a single Class C network address with subnets for LANs and WANs 
  •  Assign IP addresses to router interfaces and hosts
  •  Diagram the network using ConfigMaker

Background:

In this lab you will work with other group members to design a 5-router network topology and an IP addressing scheme. You must come up with a proper IP addressing scheme using a single Class C network address (204.204.7.0) and multiple subnets. You will then use ConfigMaker to make a diagram of the network you have designed. You have creative freedom in designing your network.

Tools / Preparation:

Prior to starting this lab you should have the equipment for the standard 5-router lab available (routers, hubs, switches, cables, etc.). Since this is a challenge lab, the routers may or may not be pre-configured with the correct IP interface settings etc. If they are, you will need to change the IP addresses to be different form those of the standard lab setup. The workstations may also be pre-configured to have the correct IP address settings prior to starting the lab. The IP addressing configuration of the workstations will also need to be changed. If the actual lab equipment is not available to configure, design the network using the worksheets provided in this lab. Work in teams of 5 or more.


The following resources will be required:

  •  5 PC workstations (min.) with Windows operating system and HyperTerminal installed.
  •  5 Cisco Routers (model 1600 series or 2500 series with IOS 11.2 or later).
  •  4 Ethernet hubs (10BASE-T with 4 to 8 ports).
  •  One Ethernet switch (Cisco Catalyst 1900 or comparable).
  •  5 serial console cables to connect workstation to router console port (with RJ-45 to DB9 converters).
  •  4 Sets of V.35 WAN serial cables (DTE male/ DCE female) to connect from router to router.
  • CAT5 Ethernet Cables wired straight through to connect routers and workstations to hubs and switches.
  •  AUI (DB15) to RJ-45 Ethernet transceivers (Quantity depends on the number of routers with AUI ports) to convert router AUI interfaces to 10BASE-T RJ-45.

Websites Sites Required:       

Routing basics
General information on routers 
2500 series routers 
1600 series routers 
Terms and acronyms
IP routing protocol IOS command summary

Notes:

 


Step 1 - Design the physical topology of the network.

You should have at least 5 routers in different geographical locations. You should have at least one Ethernet LAN off of each router. Sketch out the topology as you go. Answer the following questions to assist in planning:

1. How many routers will you have?
 

2. Where will the routers be located?
 

3. How many switches will you have?
 

Step 2 - Develop an IP addressing scheme.

Review your topology sketch from step one. Using a single Class C address of 204.204.7.0, create a subnetwork design for your topology. Document your scheme by indicating where you will put each of the subnets. Answer the following questions to assist in planning.

4. How many LANs are there?
 

5. How many WANs are there?
 

6. How many unique subnets will you need?
 

7. How many hosts per subnet (LAN and WAN) will you have?
 

8. How many IP addresses (hosts + router interfaces) will be required?
 

9. What is your Class C network address?
 

10. How many bits will you borrow from the host portion of the network address?  

11. What will your subnet mask be?
 

12. How many total useable subnets will this allow for?  

13. How many hosts per subnet will this allow for?
 

Step 3 - Assign IP addresses to each device interface.

Using the table assign an IP address to each device interface or range of devices (hosts) that will require an IP address. Switches do not require an IP address but you may assign one if you want to. Hubs will not have an IP address. (answers will vary)

Device name / model Interface IP address Subnet mask Default gateway
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         

14. Which interfaces will require clock rate to be set? 

Step 4 - Diagram the network using ConfigMaker.

Use Cisco ConfigMaker to create a network diagram and add all configuration information such as IP addresses and subnet masks. ConfigMaker will allow you to enter all interface IP addresses and help you create a finished diagram. You should be familiar with ConfigMaker if you have completed lab 6.5.2.2. Use the web site listed in the overview section to download ConfigMaker if you do not have it.

Reflection:
 
 
 
 
 

 

Content

 

Lab 10.4.1 Topology challenge lab 

Estimated time: 30 min.

Objectives:

  • Design an IP addressing scheme based on a given network topology 
  • Use multiple Class C network addresses for LANs and WANs 
  • Assign IP addresses to router interfaces 
  • Diagram the network using ConfigMaker

Background:

You and your group members have just received your Cisco certification. Your first job is to work with other group members in designing a topology and IP addressing scheme. It will be a 5-router topology similar to the standard 5-router lab diagram as shown but with a few changes.  Refer to the modified 5-router lab diagram shown in the worksheet. You must come up with a proper IP addressing scheme using multiple Class C addresses which are different from those of the standard lab setup. You will then use ConfigMaker to do your own diagram of the network. You may do this lab using the worksheets or work with the actual lab equipment if it is available.

Tools / Preparation:

Prior to starting this lab you should have the equipment for the standard 5-router lab available (routers, hubs, switches, cables, etc.). Since this is a challenge lab, the routers may or may not be configured with IP interface settings etc. If they are, you will need to change the IP addresses to be different from those of the standard lab setup. The IP address configuration of the workstations will also need to be changed. If the actual lab equipment is not available to configure, design the network using the worksheets provided in this lab. Work in teams of 5 or more.

The following resources will be required:

  • 5 PC workstations (min.) with Windows operating system and HyperTerminal installed. 
  • 5 Cisco Routers (model 1600 series or 2500 series with IOS 11.2 or later). 
  • 4 Ethernet hubs (10BASE-T with 4 to 8 ports).
  • One Ethernet switch (Cisco Catalyst 1900 or comparable).
  • 5 serial console cables to connect workstation to router console port (with RJ-45 to DB9 converters).
  • 4 Sets of V.35 WAN serial cables (DTE male/ DCE female) to connect from router to router.
  • CAT5 Ethernet Cables wired straight through to connect routers and workstations to hubs and switches.
  • AUI (DB15) to RJ-45 Ethernet transceivers (Quantity depends on the number of routers with AUI ports) to convert router AUI interfaces to 10BASE-T RJ-45.
  • Cisco ConfigMaker software (version 2.3 or later) See below for web site.

Websites Sites Required:

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary
 

Notes:


Step 1 - Review the physical connections on the standard lab setup.

Review the standard semester 2 lab diagram in the overview section of this lab and check all physical devices, cables and connections if the physical lab setup is available.

Step 2 - Develop an IP addressing scheme.

With the standard 5-router lab configuration shown in the overview section, there are eight (8) networks. Five (5) of these are Ethernet Local Area Networks (LANs) and 3 of them are serial Wide Area Networks (WANs). Review the modified setup of the lab diagrammed below. Using multiple Class C addresses similar to the existing standard lab, select addresses and document the IP addressing scheme by indicating where you will put each of the Class C addresses. Answer the following questions to assist your team in planning the network IP address scheme.

1. How many LANs are there?

2. How many WANs are there?

3. How many unique Class C network addresses will you need?

4. How many devices are there?

5. How many device interfaces will require IP addresses?


Step 3 – Assign IP addresses to each device interface .

Use the table below to identify each router interface that will require an IP address.  Switches do not require an IP address but you may assign one if you want to.  Hubs will not have an IP address.

Device name /
model
Interface IP Address Subnet mask Default gateway
         
         
         
         
         
         
         
         
         
         
         
         
         
         

6. Which interfaces will require clock rate to be set?

Step 4 - Diagram the network using ConfigMaker.

Use Cisco ConfigMaker to recreate the network diagram in the worksheet and add all configuration information such as IP addresses and subnet masks. ConfigMaker will allow you to enter all interface IP addresses and help you create a finished diagram. Choose your own device names. You should be familiar with ConfigMaker if you have completed lab 6.5.2.2.

Reflection: 

What did you learn from designing a topology with such a large group of people?

In what router mode did you spend most of your time?

Could you have done it any other way? If so how?







When doing this lab, how could a TFTP server have been useful?

 

Content
Overview

In "IP Addressing," you learned the process of configuring Internet Protocol (IP) addresses. In this chapter, you will learn about the router's use and operations in performing the key internetworking function of the Open System Interconnection (OSI) reference model's network layer, Layer 3. In addition, you will learn the difference between routing and routed protocols and how routers track distance between locations. Finally, you will learn about distance-vector, link-state, and hybrid routing approaches and how each resolves common routing problems.

 

Content
11.1 Routing Basics
11.1.1 Path determination
Path determination, for traffic going through a network cloud, occurs at the network layer (Layer 3). The path determination function enables a router to evaluate the available paths to a destination and to establish the preferred handling of a packet. Routing services use network topology information when evaluating network paths. This information can be configured by the network administrator or collected through dynamic processes running in the network.

The network layer provides best-effort end-to-end packet delivery across interconnected networks. The network layer uses the IP routing table to send packets from the source network to the destination network. After the router determines which path to use, it proceeds with forwarding the packet. It takes the packet that it accepted on one interface and forwards it to another interface or port that reflects the best path to the packet's destination. -

 

Content
11.1 Routing Basics
11.1.2 How routers route packets from source to destination
To be truly practical, a network must consistently represent the paths available between routers. As Figure shows, each line between the routers has a number that the routers use as a network address. These addresses must convey information that can be used by a routing process to pass packets from a source toward a destination. Using these addresses, the network layer can provide a relay connection that interconnects independent networks.

The consistency of Layer 3 addresses across the entire internetwork also improves the use of bandwidth by preventing unnecessary broadcasts. Broadcasts invoke unnecessary process overhead and waste capacity on any devices or links that do not need to receive the broadcasts. By using consistent end-to-end addressing to represent the path of media connections, the network layer can find a path to the destination without unnecessarily burdening the devices or links on the internetwork with broadcasts.

 

Content
11.1 Routing Basics
11.1.3 Network and host addressing
The router uses the network address to identify the destination network (LAN) of a packet within an internetwork. The graphic shows three network numbers identifying segments connected to the router.

For some network layer protocols, this relationship is established by a network administrator who assigns network host addresses according to a predetermined internetwork addressing plan. For other network layer protocols, assigning host addresses is partially or completely dynamic. Most network protocol addressing schemes use some form of a host or node address. In the graphic, three hosts are shown sharing the network number 1. -

 

Content
11.1 Routing Basics
11.1.4 Path selection and packet switching
A router generally relays a packet from one data link to another, using two basic functions:
  • a path determination function
  • a switching function. 

Figure illustrates how routers use addressing for these routing and switching functions. The router uses the network portion of the address to make path selections to pass the packet to the next router along the path.

The switching function allows a router to accept a packet on one interface and forward it through a second interface. The path determination function enables the router to select the most appropriate interface for forwarding a packet. The node portion of the address is used by the final router (the router connected to the destination network) to deliver the packet to the correct host.

 

Content
11.1 Routing Basics
11.1.5 Routed versus routing protocol
Because of the similarity of the two terms, confusion often exists with routed protocol and routing protocol.

Routed protocol is any network protocol that provides enough information in its network layer address to allow a packet to be forwarded from one host to another host based on the addressing scheme. Routed protocols define the field formats within a packet. Packets are generally conveyed from end system to end system. The Internet Protocol (IP) is an example of a routed protocol.

Routing protocols support a routed protocol by providing mechanisms for sharing routing information. Routing protocol messages move between the routers. A routing protocol allows the routers to communicate with other routers to update and maintain tables. TCP/IP examples of routing protocols are:

  • RIP (Routing Information Protocol)
  • IGRP (Interior Gateway Routing Protocol)
  • EIGRP (Enhanced Interior Gateway Routing Protocol)
  • OSPF (Open Shortest Path First)

 

Content
11.1 Routing Basics
11.1.6 Network-layer protocol operations
When a host application needs to send a packet to a destination on a different network, the host addresses the data link frame to the router, using the address of one of the router's interfaces. The router's network layer process examines the incoming packet's header to determine the destination network, and then references the routing table which associates networks to outgoing interfaces.  The packet is encapsulated again in the data link frame that is appropriate for the selected interface, and queued for delivery to the next hop in the path.

This process occurs each time that the packet is forwarded through another router. At the router that is connected to the destination host's network, the packet is encapsulated in the destination LAN's data link frame type and delivered to the destination host.

 

Content
11.1 Routing Basics
11.1.7 Multiprotocol routing
Routers are capable of supporting multiple independent routing protocols and maintaining routing tables for several routed protocols. This capability allows a router to deliver packets from several routed protocols over the same data links.

 

Content
11.2 Why Routing Protocols are Necessary
11.2.1 Static versus dynamic routes
Static route knowledge is administered manually by a network administrator who enters it into a router's configuration. The administrator must manually update this static route entry whenever an internetwork topology change requires an update.

Dynamic route knowledge works differently. After a network administrator enters configuration commands to start dynamic routing, the route knowledge is automatically updated by a routing process whenever new information is received from the internetwork. Changes in dynamic knowledge are exchanged between routers as part of the update process.

 

Content
11.2 Why Routing Protocols are Necessary
11.2.2 Why use a static route
Static routing has several useful applications. Dynamic routing tends to reveal everything known about an internetwork, for security reasons, you may want to hide parts of an internetwork. Static routing enables you to specify the information you want to reveal about restricted networks. 

When a network is accessible by only one path, a static route to the network can be sufficient. This type of network is called a stub network. Configuring static routing to a stub network avoids the overhead of dynamic routing.

 

Content
11.2 Why Routing Protocols are Necessary
11.2.3 How a default route is used
The Figure shows a use for a default route - a routing table entry that directs packets to the next hop when that hop is not explicitly listed in the routing table. You can set default routes as part of the static configuration.

In this example, the company X routers possess specific knowledge of the topology of the company X network, but not of other networks. Maintaining knowledge of every other network accessible by way of the Internet cloud is unnecessary and unreasonable, if not impossible. Instead of maintaining specific network knowledge, each router in company X is informed of the default route that it can use to reach any unknown destination by directing the packet to the Internet.

 

Content
11.2 Why Routing Protocols are Necessary
11.2.4
Why dynamic routing is necessary
The network shown in the Figure adapts differently to topology changes depending on whether it uses statically or dynamically configured routing information.

Static routing allows routers to properly route a packet from network to network based on configured information. The router refers to its routing table and follows the static knowledge residing there to relay the packet to Router D. Router D does the same, and relays the packet to Router C. Router C delivers the packet to the destination host.

If the path between Router A and Router D fails, Router A will not be able to relay the packet to Router D using that static route. Until Router A is manually reconfigured to relay packets by way of Router B, communication with the destination network is impossible.

Dynamic routing offers more flexibility. According to the routing table generated by Router A, a packet can reach its destination over the preferred route through Router D. However, a second path to the destination is available by way of Router B. When Router A recognizes that the link to Router D is down, it adjusts its routing table, making the path through Router B the preferred path to the destination. The routers continue sending packets over this link.

When the path between Routers A and D is restored to service, Router A can once again change its routing table to indicate a preference for the counterclockwise path through Routers D and C to the destination network. Dynamic routing protocols can also direct traffic from the same session over different paths in a network for better performance. This is known as loadsharing.

 

Content
11.2 Why Routing Protocols are Necessary
11.2.5 Dynamic routing operations
The success of dynamic routing depends on two basic router functions:
  • maintenance of a routing table
  • timely distribution of knowledge, in the form of routing updates, to other routers 

Dynamic routing relies on a routing protocol to share knowledge among routers. A routing protocol defines the set of rules used by a router when it communicates with neighboring routers. For example, a routing protocol describes:

  • how to send updates
  • what knowledge is contained in these updates
  • when to send this knowledge
  • how to locate recipients of the updates

 

Content
11.2 Why Routing Protocols are Necessary
11.2.6
How distances on network paths are determined by various metrics
When a routing algorithm updates a routing table, its primary objective is to determine the best information to include in the table. Each routing algorithm interprets what is best in its own way. The algorithm generates a number, called the metric value, for each path through the network. Typically, the smaller the metric number, the better the path.

You can calculate metrics based on a single characteristic of a path; you can calculate more complex metrics by combining several characteristics. The metrics most commonly used by routers are as follows:

  • bandwidth -- the data capacity of a link; (normally, a 10 Mbps Ethernet link is preferable to a 64 kbps leased line)
  • delay -- the length of time required to move a packet along each link from source to destination
  • load -- the amount of activity on a network resource such as a router or link
  • reliability -- usually refers to the error rate of each network link
  • hop count -- the number of routers a packet must travel through before reaching its destination
  • ticks -- the delay on a data link using IBM PC clock ticks (approximately 55 milliseconds).
  • cost -- an arbitrary value, usually based on bandwidth, monetary expense, or other measurement, that is assigned by a network administrator

 

Content
11.2 Why Routing Protocols are Necessary
11.2.7 Three classes of routing protocols
Most routing algorithms can be classified as one of two basic algorithms:
  • distance vector; or 
  • link state. 

The distance-vector routing approach determines the direction (vector) and distance to any link in the internetwork. The link-state (also called shortest path first) approach re-creates the exact topology of the entire internetwork (or at least the portion in which the router is situated). 

The balanced hybrid approach combines aspects of the link-state and distance-vector algorithms. The next several pages cover procedures and problems for each of these routing algorithms and present techniques for minimizing the problems.

 

Content
11.2 Why Routing Protocols are Necessary
11.2.8 Time to convergence
The routing algorithm is fundamental to dynamic routing. Whenever the topology of a network changes because of growth, reconfiguration, or failure, the network knowledge base must also change. The knowledge needs to reflect an accurate, consistent view of the new topology. This view is called convergence.

When all routers in an internetwork are operating with the same knowledge, the internetwork is said to have converged. Fast convergence is a desirable network feature because it reduces the period of time in which routers would continue to make incorrect/wasteful routing decisions.

 

Content
11.3 Distance-Vector Routing
11.3.1 Distance-vector routing basics
Distance-vector-based routing algorithms pass periodic copies of a routing table from router to router. These regular updates between routers communicate topology changes.

Each router receives a routing table from its directly connected neighboring routers. For example, in the graphic, Router B receives information from Router A. Router B adds a distance-vector number (such as a number of hops), which increases the distance vector and then passes this new routing table to its other neighbor, Router C. This same step-by-step process occurs in all directions between direct-neighbor routers.

The algorithm eventually accumulates network distances so that it can maintain a database of network topology information. Distance-vector algorithms do not, however, allow a router to know the exact topology of an internetwork.

 

Content
11.3 Distance-Vector Routing
11.3.2
How distance-vector protocols exchange routing tables
Each router that uses distance-vector routing begins by identifying its own neighbors. In the Figure, the interface that leads to each directly-connected network is shown as having a distance of 0. As the distance-vector network discovery process proceeds, routers discover the best path to destination networks based on the information they receive from each neighbor. For example, Router A learns about other networks based on the information that it receives from Router B. Each of the other network entries in the routing table has an accumulated distance vector to show how far away that network is in a given direction.

 

Content
11.3 Distance-Vector Routing
11.3.3 How topology changes propagate through the network of routers
When the topology in a distance-vector protocol network changes, routing table updates must occur. As with the network discovery process, topology change updates proceed step-by-step from router to router. Distance-vector algorithms call for each router to send its entire routing table to each of its adjacent neighbors. The routing tables include information about the total path cost (defined by its metric) and the logical address of the first router on the path to each network contained in the table.

 

Content
11.3 Distance-Vector Routing
11.3.4 The problem of routing loops
Routing loops can occur if a network's slow convergence on a new configuration causes inconsistent routing entries. The Figure illustrates how a routing loop can occur:
  1. Just before the failure of Network 1, all routers have consistent knowledge and correct routing tables. The network is said to have converged. Assume for the remainder of this example that Router C's preferred path to Network 1 is by way of Router B, and the distance from Router C to Network 1 is 3.
  2. When Network 1 fails, Router E sends an update to Router A. Router A stops routing packets to Network 1, but Routers B, C, and D continue to do so because they have not yet been informed of the failure. When Router A sends out its update, Routers B and D stop routing to Network 1; however, Router C has not received an update. To Router C, Network 1 is still reachable via Router B. 
  3. Now Router C sends a periodic update to Router D, indicating a path to Network 1 by way of Router B. Router D changes its routing table to reflect this good, but incorrect, information, and propagates the information to Router A. Router A propagates the information to Routers B and E, and so on. Any packet destined for Network 1 will now loop from Router C to B to A to D and back to again to C.

 

Content
11.3 Distance-Vector Routing
11.3.5 The problem of counting to infinity
Continuing the example from the previous page, the invalid updates of Network 1 will continue to loop until some other process stops the looping. This condition, called count to infinity, loops packets continuously around the network in spite of the fundamental fact that the destination network, Network 1, is down. While the routers are counting to infinity, the invalid information allows a routing loop to exist. 

Without countermeasures to stop the process, the distance vector (metric) of hop count increments each time the packet passes through another router. These packets loop through the network because of wrong information in the routing tables.

 

Content
11.3 Distance-Vector Routing
11.3.6 The solution of defining a maximum
Distance-vector routing algorithms are self-correcting, but a routing loop problem can require a count to infinity first. To avoid this prolonged problem, distance-vector protocols define infinity as a specific maximum number. This number refers to a routing metric (e.g. a simple hop count). 

With this approach, the routing protocol permits the routing loop to continue until the metric exceeds its maximum allowed value. The graphic shows the metric value as 16 hops, which exceeds the distance-vector default maximum of 15 hops, and the packet is discarded by the router. In any case, when the metric value exceeds the maximum value, Network 1 is considered unreachable.

 

Content
11.3 Distance-Vector Routing
11.3.7 The solution of split horizon
Another possible source for a routing loop occurs when incorrect information that has been sent back to a router contradicts the correct information that it sent. Here is how this problem occurs: 
  1. Router A passes an update to Router B and Router D, indicating that Network 1 is
    down. Router C, however, transmits an update to Router B, indicating that Network 1 is available at a distance of 4, by way of Router D. This does not violate split-horizon rules.
  2. Router B concludes, incorrectly, that Router C still has a valid path to Network 1, although at a much less favorable metric. Router B sends an update to Router A advising Router A of the new route to Network 1. 
  3. Router A now determines that it can send to Network 1 by way of Router B; Router B determines that it can send to Network 1 by way of Router C; and Router C determines that it can send to Network 1 by way of Router D. Any packet introduced into this environment will loop between routers. 
  4. Split-horizon attempts to avoid this situation. As shown in the Figure , if a routing update about Network 1 arrives from Router A, Router B or Router D cannot send information about Network 1 back to Router A. Split-horizon thus reduces incorrect routing information and reduces routing overhead.

 

Content
11.3 Distance-Vector Routing
11.3.8 The solution of hold-down timers
You can avoid a count to infinity problem by using hold-down timers that work as follows: 
  1. When a router receives an update from a neighbor indicating that a previously accessible network is now inaccessible, the router marks the route as inaccessible and starts a hold-down timer. If at any time before the hold-down timer expires an update is received from the same neighbor indicating that the network is again accessible, the router marks the network as accessible and removes the hold-down timer. 
  2. If an update arrives from a different neighboring router with a better metric than originally recorded for the network, the router marks the network as accessible and removes the hold-down timer. 
  3. If at any time before the hold-down timer expires an update is received from a different neighboring router with a poorer metric, the update is ignored. Ignoring an update with a poorer metric when a hold-down timer is in effect allows more time for the knowledge of a disruptive change to propagate through the entire network.

 

Content
11.4 Link-State Routing
11.4.1 Link-state routing basics
The second basic algorithm used for routing is the link-state algorithm. Link-state based routing algorithms, also known as SPF (shortest path first) algorithms, maintain a complex database of topology information. Whereas the distance-vector algorithm has nonspecific information about distant networks and no knowledge of distant routers, a link-state routing algorithm maintains full knowledge of distant routers and how they interconnect. Link-state routing uses:
  • link-state advertisements (LSAs)
  • a topological database
  • the SPF algorithm, and the resulting SPF tree
  • a routing table of paths and ports to each network

Engineers have implemented this link-state concept in OSPF (Open Shortest Path First) routing. RFC 1583 contains a description of OSPF link-state concepts and operations.

 

Content
11.4 Link-State Routing
11.4.2
How link-state protocols exchange routing tables
Network discovery for link-state routing uses the following processes:
  1. Routers exchange LSAs with each other. Each router begins with directly connected networks for which it has direct information.
  2. Each router in parallel with the others constructs a topological database consisting of all the LSAs from the internetwork.
  3. The SPF algorithm computes network reachability. The router constructs this logical topology as a tree, with itself as root, consisting of all possible paths to each network in the link-state protocol internetwork. It then sorts these paths shortest path first (SPF).
  4. The router lists its best paths, and the ports to these destination networks, in the routing table. It also maintains other databases of topology elements and status details.

 

Content
11.4 Link-State Routing
11.4.3 How topology changes propagate through the network of routers
Link-state algorithms rely on using the same link-state updates. Whenever a link-state topology changes, the routers that first become aware of the change send information to other routers or to a designated router that all other routers can use for updates. This involves sending common routing information to all routers in the internetwork. To achieve convergence, each router does the following:
  • keeps track of its neighbors: each neighbor's name, whether the neighbor is up or down, and the cost of the link to the neighbor.
  • constructs an LSA packet that lists its neighbor router names and link costs, including new neighbors, changes in link costs, and links to neighbors that have gone down.
  • sends out this LSA packet so that all other routers receive it.
  • when it receives an LSA packet, records the LSA packet in its database so that it updates the most recently generated LSA packet from each router.
  • completes a map of the internetwork by using accumulated LSA packet data and then computes routes to all other networks by using the SPF algorithm.

Each time an LSA packet causes a change to the link-state database, the link-state algorithm (SPF) recalculates the best paths and updates the routing table. Then, every router takes the topology change into account as it determines the shortest path to use for packet routing.

Web Links
Dijkstra's algorithm

 

 

Content
11.4 Link-State Routing
11.4.4 Two link-state concerns
There are two link-state concerns - processing and memory requirements, and bandwidth requirements.

Processing and memory requirements
Running link-state routing protocols in most situations requires that routers use more memory and perform more processing than distance-vector routing protocols. Network administrators must ensure that the routers they select are capable of providing these necessary resources.

Routers keep track of all other routers in a group and the networks that they can each reach directly. For link-state routing, their memory must be able to hold information from various databases, the topology tree, and the routing table. Using Dijkstra's algorithm to compute the SPF requires a processing task proportional to the number of links in the internetwork, multiplied by the number of routers in the internetwork.

Bandwidth requirements
Another cause for concern involves the bandwidth that must be consumed for initial link-state packet flooding. During the initial discovery process, all routers using link-state routing protocols send LSA packets to all other routers. This action floods the internetwork as routers make their en masse demand for bandwidth, and temporarily reduce the bandwidth available for routed traffic that carries user data. After this initial flooding, link-state routing protocols generally require only minimal bandwidth to send infrequent or event-triggered LSA packets that reflect topology changes.

 

Content
11.4 Link-State Routing
11.4.5
Unsynchronized link-state advertisements (LSAs) leading to inconsistent path decisions amongst routers
The most complex and important aspect of link-state routing is making sure that all routers get all necessary LSA packets. Routers with different sets of LSAs calculate routes based on different topological data. Then, networks become unreachable as a result of a disagreement among routers about a link. Following is an example of inconsistent path information:
  1. Between Routers C and D, Network 1 goes down. Both routers construct an LSA packet to reflect this unreachable status.
  2. Soon afterward, Network 1 comes back up; another LSA packet reflecting this next topology change is needed.
  3. If the original "Network 1, Unreachable" message from Router C uses a slow path for its update, that update comes later. This LSA packet can arrive at Router A after Router D's "Network 1, Back Up Now" LSA.
  4. With unsynchronized LSAs, Router A can face a dilemma about which SPF tree to construct. Should it use paths that include Network 1, or paths without Network 1, which was most recently reported as unreachable?

If LSA distribution to all routers is not done correctly, link-state routing can result in invalid routes. Scaling up with link-state protocols on very large internetworks can expand the problem of faulty LSA packet distribution. If one part of the network comes up first with other parts coming up later, the order for sending and receiving LSA packets will vary. This variation can alter and impair convergence. Routers might learn about different versions of the topology before they construct their SPF trees and routing tables. On a large internetwork, parts that update more quickly can cause problems for parts that update more slowly.

 

Content
11.5 The Context of Different Routing Protocols
11.5.1 Distance-vector versus link-state routing protocols
You can compare distance-vector routing to link-state routing in several key areas:
  • Distance-vector routing gets topological data from the routing table information of its neighbors. Link-state routing obtains a wide view of the entire internetwork topology by accumulating all necessary LSAs.
  • Distance-vector routing determines the best path by adding to the metric value that it receives as routing information is passed from router to router. For link-state routing, each router works separately to calculate its own shortest path to destination networks.
  • With most distance-vector routing protocols, updates for topology changes come in periodic table updates. The information passes from router to router, usually resulting in slower convergence. With link-state routing protocols, updates are usually triggered by topology changes. Relatively small LSAs passed to all other routers usually result in faster time to converge on any internetwork topology change.

 

Content
11.5 The Context of Different Routing Protocols
11.5.2 Hybrid routing protocols
An emerging third type of routing protocol combines aspects of both distance-vector and link-state routing. This third type is called balanced-hybrid routing. Balanced-hybrid routing protocols use distance vectors with more accurate metrics to determine the best paths to destination networks. However, they differ from most distance-vector protocols by using topology changes to trigger routing database updates.

The balanced-hybrid routing protocol converges rapidly, like the link-state protocols. However, it differs from distance-vector and link-state protocols by using fewer resources such as bandwidth, memory, and processor overhead. Examples of hybrid protocols are OSI's IS-IS (Intermediate System-to-Intermediate System), and Cisco's EIGRP (Enhanced Interior Gateway Routing Protocol).

 

Content
11.5 The Context of Different Routing Protocols
11.5.3 LAN-to-LAN routing
The network layer must understand and be able to interface with various lower layers. Routers must be capable of seamlessly handling packets encapsulated into various lower-level frames without changing the packets' Layer 3 addressing.

The Figure shows an example of this with LAN-to-LAN routing. In this example, packet traffic from source Host 4 on Ethernet Network 1 needs a path to destination Host 5 on Network 2. The LAN hosts depend on the router and its consistent network addressing to find the best path.

When the router checks its routing table entries, it discovers that the best path to destination Network 2 uses outgoing port To0, the interface to a token-ring LAN. Although the lower-layer framing must change as the router passes packet traffic from Ethernet on Network 1 to token-ring on Network 2, the Layer 3 addressing for source and destination remains the same. In the Figure, the destination address remains Network 2, Host 5, regardless of the different lower-layer encapsulations.

 

Content
11.5 The Context of Different Routing Protocols
11.5.4 LAN-to-WAN routing
The network layer must relate to, and interface with, various lower layers for LAN-to-WAN traffic. As an internetwork grows, the path taken by a packet may encounter several relay points and a variety of data link types beyond the LANs. For example, in the Figure, the following takes place:
  1. A packet from the top workstation at address 1.3 must traverse three data links to reach the file server at address 2.4, shown on the bottom.
  2. The workstation sends a packet to the file server by first encapsulating it in a token-ring frame addressed to Router A.
  3. When Router A receives the frame, it removes the packet from the token-ring frame, encapsulates it in a Frame Relay frame, and forwards the frame to Router B.
  4. Router B removes the packet from the Frame Relay frame and forwards it to the file server in a newly created Ethernet frame.
  5. When the file server at 2.4 receives the Ethernet frame, it extracts and passes the packet to the appropriate upper-layer process.

Routers enable LAN-to-WAN packet flow by keeping the end-to-end source and destination addresses constant while encapsulating the packet in data link frames, as appropriate, for the next hop along the path.

 

Content
11.5 The Context of Different Routing Protocols
11.5.5 Path selection and switching of multiple protocols and media
Routers are devices that implement the network service. They provide interfaces for a wide range of links and subnetworks at a wide range of speeds. Routers are active and intelligent network nodes that can participate in managing a network. Routers manage networks by providing dynamic control over resources and supporting the tasks and goals for internetwork connectivity, reliable performance, management control, and flexibility.

In addition to the basic switching and routing functions, routers have a variety of additional features that help to improve the cost-effectiveness of the internetwork. These features include sequencing traffic based on priority and traffic filtering.

Typically, routers are required to support multiple protocol stacks, each with its own routing protocols, and to allow these different environments to operate in parallel. In practice, routers also incorporate bridging functions and sometimes serve as a limited form of hub.

 

Content
Summary
In this chapter, you learned that:
  • Internetworking functions of the network layer include network addressing and best path selection for traffic.
  • In network addressing, one part of the address is used to identify the path used by the router and the other is used for ports or devices on the network.
  • Routed protocols allow routers to direct user traffic; routing protocols work between routers to maintain routing tables.
  • Network discovery for distance-vector routing involves exchange of routing tables; problems can include slow convergence.
  • For link-state routing, routers calculate the shortest paths to other routers; problems can include inconsistent updates.
  • Balanced hybrid routing uses attributes of both link-state and distance-vector routing.

 

Content
Overview
Now that you have learned about routing protocols, you are ready to configure IP routing protocols. As you know, routers can be configured to use one or more IP routing protocols. In this chapter, you will learn about the initial configuration of the router to enable the IP routing protocols of Routing Information Protocol (RIP) and Interior Gateway Routing Protocol (IGRP). In addition, you will learn how to monitor IP routing protocols.

 

12.1 Initial Router Configuration
12.1.1 Setup mode
After testing the hardware and loading the Cisco IOS system image, the router finds and applies the configuration statements. These entries provide the router with details about router-specific attributes, protocol functions, and interface addresses. However, if the router is unable to locate a valid startup-config file, it enters an initial router configuration mode called setup mode

With the setup mode command facility, you can answer questions in the system configuration dialog. This facility prompts you for basic configuration information. The answers you enter allow the router to use a sufficient, but minimal-feature, router configuration that includes the following: 

  • an inventory of interfaces
  • an opportunity to enter global parameters
  • an opportunity to enter interface parameters
  • a setup script review
  • an opportunity to indicate whether you want the router to use this configuration

After you approve setup mode entries, the router uses the entries as a running configuration. The router also stores the configuration in NVRAM as a new startup-config, and you can start using the router. For additional protocol and interface changes, you can use the enable mode and enter the command configure.

 

12.1 Initial Router Configuration
12.1.2 Initial IP routing table
Initially, a router must refer to entries about networks or subnets that are directly connected to it. Each interface must be configured with an IP address and a mask. The Cisco IOS software learns about this IP address and mask information from a configuration that has been input from some source. The initial source of addressing is a user who types it into a configuration file. 

In the lab that follows, you will start up your router in a just-received condition, a state that lacks another source for the startup configuration. This condition on the router will permit you to use the setup-mode command facility and answer prompts for basic configuration information. The answers you enter will include address-to-port commands to set up router interfaces for IP.

 

12.1 Initial Router Configuration
12.1.3 How a router learns about destinations

By default, routers learn paths to destinations three different ways :

  • static routes -- manually defined by the system administrator as the next hop to a destination; useful for security and traffic reduction
  • default routes -- manually defined by the system administrator as the path to take when there is no known route to the destination
  • dynamic routing -- the router learns of paths to destinations by receiving periodic updates from other routers.
12.1 Initial Router Configuration
12.1.4 The ip route command

The ip route command sets up a static route. -

The administrative distance is a rating of the trustworthiness of a routing information source, expressed as a numeric value from 0 to 255. The higher the number, the lower the trustworthiness rating.

A static route allows manual configuration of the routing table. No dynamic changes to this table entry will occur as long as the path is active. A static route may reflect some special knowledge of the networking situation known to the network administrator. Manually-entered administrative distance values for static routes are usually low numbers (1 is the default). Routing updates are not sent on a link if they are only defined by a static route, therefore, they conserve bandwidth.

 

12.1 Initial Router Configuration
12.1.5 Using the ip route command

The assignment of a static route to reach the stub network 172.16.1.0 is proper for Cisco A because there is only one way to reach that network. The assignment of a static route from Cisco B to the cloud networks is also possible. However, a static route assignment is required for each destination network, in which case a default route may be more appropriate. -

Lab Activity
   In this lab you will configure a static route between neighboring routers.

 

12.1 Initial Router Configuration
12.1.6 The ip default-network command

The ip default-network command establishes a default route in networks using dynamic routing protocols.. -

Default routes keep routing tables shorter. When an entry for a destination network does not exist in a routing table, the packet is sent to the default network. Because a router does not have complete knowledge about all destination networks, it can use a default network number to indicate the direction to take for unknown network numbers. Use the default network number when you need to locate a route but have only partial information about the destination network. The ip default-network command must be added to all routers in the network or used with the additional command redistribute static so all networks have knowledge of the candidate default network.

 

12.1 Initial Router Configuration
12.1.7 Using the ip default-network command

In the example, the global command ip default-network 192.168.17.0 defines the Class C network 192.168.17.0 as the destination path for packets that have no routing table entries. The Company X administrator does not want updates coming in from the public network. Router A could need a firewall for routing updates. Router A may need a mechanism to group those networks that will share Company X's routing strategy. One such mechanism is an autonomous system number.

 

12.2 Interior and Exterior Routing Protocols
12.2.1 Autonomous system
An autonomous system consists of routers, run by one or more operators, that present a consistent view of routing to the external world. The Network Information Center (NIC) assigns a unique autonomous system to enterprises. This autonomous system is a 16 bit number. A routing protocol such as Cisco's IGRP requires that you specify this unique, assigned autonomous system number in your configuration.

 

12.2 Interior and Exterior Routing Protocols
12.2.2 Interior versus exterior routing protocols
Exterior routing protocols are used for communications between autonomous systems. Interior routing protocols are used within a single autonomous system.
12.2 Interior and Exterior Routing Protocols
12.2.3 Interior IP routing protocols
At the Internet layer of the TCP/IP suite of protocols, a router can use an IP routing protocol to accomplish routing through the implementation of a specific routing algorithm. Examples of IP routing protocols include:
  • RIP -- a distance-vector routing protocol
  • IGRP -- Cisco's distance-vector routing protocol
  • OSPF -- a link-state routing protocol 
  • EIGRP -- a balanced hybrid routing protocol

The following sections show you how to configure the first two of these protocols.

 

12.2 Interior and Exterior Routing Protocols
12.2.4 IP routing configuration tasks
The selection of an IP routing protocol involves the setting of both global and interface parameters. Global tasks include selecting a routing protocol, either RIP or IGRP, and indicating IP network numbers with specifying subnet values. The interface task is to assign network/subnet addresses and the appropriate subnet mask. Dynamic routing uses broadcasts and multicasts to communicate with other routers. The routing metric helps routers find the best path to each network or subnet.

 

12.2 Interior and Exterior Routing Protocols
12.2.5 Using the router and network commands
The router command starts a routing process.

The network command is required because it enables the routing process to determine which interfaces will participate in the sending and receiving of routing updates.

The network numbers must be based on the network class addresses, not subnet addresses or individual host addresses. Major network addresses are limited to Class A, B and C network numbers.

 

12.3 RIP
12.3.1 Key elements of RIP
RIP was originally specified in RFC 1058. Its key characteristics include the following:
  • It is a distance-vector routing protocol.
  • Hop count is used as the metric for path selection.
  • If the hop count is greater than 15, the packet will be discarded.
  • By default, routing updates are broadcast every 30 seconds.

 

12.3 RIP
12.3.2 Using router rip and network commands to enable RIP
The router rip command selects RIP as the routing protocol. The network command assigns a network class address to which a router will be directly connected. The routing process associates interfaces with the network addresses and begins using RIP on the specified networks. Note: In RIP all subnet masks must be the same. RIP does not share subnetting information in routing updates.
12.3 RIP
12.3.3 Enabling RIP on an IP-addressed network
In the example, the descriptions for the commands are as follows:
  • router rip -- selects RIP as the routing protocol
  • network 1.0.0.0 -- specifies a directly connected network
  • network 2.0.0.0 -- specifies a directly connected network

The Cisco A router interfaces that are connected to networks 1.0.0.0 and 2.0.0.0 send and receive RIP updates. These routing updates allow the router to learn the network topology.

12.3 RIP
12.3.4 Monitoring of IP packet flow using the show ip protocol command
The show ip protocol command displays values, about routing timers and network information, that are associated with the entire router. Use this information to identify a router that you suspect of delivering bad routing information.

The router in the example sends updated routing table information every 30 seconds (configured interval). Seventeen seconds have elapsed since it sent its last update; it will send the next one in 13 seconds. Following the "Routing for Networks" line, the router specifies routes for the listed networks. The last line shows that the RIP administrative distance is 120.

 

12.3 RIP
12.3.5 The show ip route command
The show ip route command displays the contents of the IP routing table, which contains entries for all known networks and subnetworks, along with a code that indicates how that information was learned.
Lab Activity
  In this lab you will configure RIP as the routing protocol.

 

12.4 IGRP
12.4.1 Key characteristics of IGRP

IGRP is a distance-vector routing protocol developed by Cisco. IGRP sends routing updates at 90 second intervals, advertising networks for a particular autonomous system. Some of the IGRP key design characteristics emphasize the following:

  • versatility that enables it to automatically handle indefinite, complex topologies
  • flexibility for segments that have different bandwidth and delay characteristics
  • scalability for functioning in very large networks

The IGRP routing protocol by default uses two metrics, bandwidth and delay. IGRP can be configured to use a combination of variables to determine a composite metric. Those variables include:

  • bandwidth
  • delay
  • load
  • reliability

 

12.4 IGRP
12.4.2 Using router igrp and network commands to enable IGRP
The router igrp command selects IGRP as a routing protocol.

The network command specifies any directly connected networks that are to be included. Note: Like RIP, all subnet masks must be the same. IGRP does not share subnetting information in routing updates.

 

12.4 IGRP
12.4.3 Enabling IGRP on an IP-addressed network
IGRP is selected as the routing protocol for autonomous system 109. All interfaces connected to networks 1.0.0.0 and 2.0.0.0 will be used to send and receive IGRP routing updates. In the example:
  • router igrp 109 -- selects IGRP as the routing protocol for autonomous system 109

  • network 1.0.0.0 -- specifies a directly connected network

  • network 2.0.0.0 -- specifies a directly connected network

 

12.4 IGRP
12.4.4 Monitoring IP packet flow using the show ip protocol command

The show ip protocol command displays parameters, filters, and network information about all of the routing protocol(s) (i.e. RIP, IGRP, etc.) in use on the router. The algorithm used to calculate the routing metric for IGRP is shown in this display. It defines the value of the K1-K5 metrics and the maximum hop count. The metric K1 represents bandwidth and the metric K3 represents delay. By default the values of the metrics K1 and K3 are set to 1. K2,K4 and K5 metric values are set to 0.

 

12.4 IGRP
12.4.5 The show ip interfaces command

The show ip interfaces command displays the status and global parameters associated with all IP interfaces. The Cisco IOS software automatically enters a directly-connected route in the routing table if the interface is one through which software can send and receive packets. Such an interface is marked up. If the interface is unusable, it is removed from the routing table. Removing the entry allows the use of backup routes, if they exist.

 

12.4 IGRP
12.4.6 The show ip route command
The show ip route command displays the contents of an IP routing table. The table contains a list of all known networks and subnets and the metrics associated with each entry. Note that in this example the information was derived from IGRP (I), or from direct connections (C).

 

12.4 IGRP
12.4.7 The debug ip rip command
The debug ip rip command displays RIP routing updates as they are sent and received. In this example, the update is sent by 183.8.128.130. It reported on three routers, one of which is inaccessible because its hop count is greater than 15. Updates were then broadcast through 183.8.128.2. 

Use caution when using debug commands. Debug commands are processor intensive and can decrease network performance or cause loss of connectivity. Use only during times of low network usage. Disable the command when finished by using the command, no debug ip rip or no debug all.

 

Content
12.5 Challenge Labs
12.5.1 Rip convergence challenge
Lab Activity
  As a system administrator, there will be times where configuring static routes can be very useful. Static routes are useful for stub networks because there is only one way to get to that network. Security is another reason to use static routes. For example, if you have a network or networks that you don't want the rest of the network to be able to "see" you would not want RIP or other routing protocols sending periodic updates to other routers. With simple networks (few routers) it is sometimes more efficient to use static routes since it conserves bandwidth on WAN links. In this lab you will use static routes for troubleshooting purposes and to see their relationship to dynamic routes and routing protocols.

 

Content
12.5 Challenge Labs
12.5.2 Routing loops setup challenge
Lab Activity
  In this lab you will setup a WAN connection between Lab-A and Lab-E to create alternate paths in the standard router lab setup. Using a set of WAN serial cables, connect Lab-A Serial 1 to Lab-E Serial 0. Remember to set the clock rate on the DCE side of the cable (Lab-E's Serial 0 interface).

 

Content
12.5 Challenge Labs
12.5.3 Preventing routing loops
Lab Activity
  In the previous challenge lab, you saw how long it took to converge when a link went down. In this lab, your task is to find out how to prevent and control routing loops. The use of hold-down timers, defining a maximum hop count, counting to infinity, poison reverse and split-horizon are all methods of controlling routing loops. You will use the RIP hop count metric to control routing loops in this lab.

 

Content
Summary
  • Initially, a router must refer to entries about networks or subnets that are directly connected.
  • Default routers learn paths to destinations three different ways:
    • Static routes
    • Default routes
    • Dynamic routes
  • The ip route command sets up a static route.
  • The ip default-network command establishes a default route.
  • Routers can be configured to use one or more IP routing protocols, such as RIP and IGRP.

 

Content

 

Lab 12.1.5 Static routes

Estimated time: 30 min.

Objectives:

  • Configure a static route between direct neighboring routers using the ip route command.
  • Copy the running configuration to startup configuration.

Background:

In this lab you will configure a static route between neighboring routers. Static routes are routes that cause packets moving between a source and a destination to take a specified path. They are typically defined manually by a network administrator. Routing updates are not sent on a link if it is only defined by a static route, thereby conserving bandwidth. Another application for a static route is security since dynamic routing tends to reveal everything known about a network. Static routes are sometimes used for remote sites and for testing of a particular link or series of routers in your internetwork.

Tools / Preparation:

Prior to starting this lab you will need to connect a PC workstation (with the HyperTerminal program loaded) to a router using the router's console interface with a roll-over (console) cable. All lab work is done through the HyperTerminal program that is configured to connect to the router. You may want to review Chapter 18 in the Cisco Networking Academy First-Year Companion Guide and review semester 2 online curriculum Chapter 12 prior to starting this lab. Work individually or in teams. Be familiar with the following command:

  • Enable 
  • Show arp 
  • Show startup-config 
  • Configure terminal 
  • IP route
  • Show running-config 
  • copy 
  • Ping

Resources Required:

  • PC with monitor, keyboard, mouse, power cords, etc. 
  • Windows operating system (Win 95, 98, NT or 2000) installed on PC 
  • HyperTerminal program configured for router console connection 
  • PC connected to the router console port with a roll-over cable

Websites Sites Required:       

Notes:

 


Step 1 – Login to router.

Explanation: Connect to the router and login.  Enter the password cisco if prompted.  

Step 2 – Test layer 3 (network) connectivity.

Task: Enter ping xxx.xxx.xxx.xxx
Explanation:
xxx.xxx.xxx.xxx is an IP address of one of your neighboring routers. 

1. Did the router’s interface respond with a successful ping?

 

Step 3 – Enter privileged mode.

Task:
         a. 
Enter enable at the command prompt.    
         b.
Enter the password of class.
Explanation:
You use the enable command to enter privileged EXEC mode.
 

Step 4 – Show the backup configuration file.

Task: Enter show startup-config (abbrev. show start) at the router prompt.
Explanation: The router will display information on the backup configuration file stored in NVRAM.

2. What routing protocols or static routes are defined, if any?

 

Step 5 – Enter global configuration mode.

Task: Enter configure terminal (abbrev.  config t) at the router prompt.
Explanation:
To configure the router you must enter the global configuration mode.  Notice how the router has changed after this command.

          3.  What does the router prompt look like?

 

Step 6 – Enter help facility.

Task: Enter IP route ? command at the router prompt.
Explanation: The router will respond with the description available for IP route. 

    4.   What was the router’s response?

 

Step 7 – Enter the help facility.

Task: Enter IP route xxx.xxx.xxx.xxx ?  at the router prompt.
Explanation: xxx.xxx.xxx.xxx is the network address for which you want a static route.
 

    5.   What was the router's response?

 

Step 8 - Enter the help facility.

Task: Enter IP route xxx.xxx.xxx.xxx yyy.yyy.yyy.yyy at the router prompt.
Explanation: xxx.xxx.xxx.xxx. is the network address of the destination network and yyy.yyy.yyy.yyy is the subnet mask of the destination network.

          6. What was the router's response?       

 

Step 9 - Enter a static route.

Task: Enter IP route xxx.xxx.xxx.xxx yyy.yyy.yyy.yyy zzz.zzz.zzz.zzz at the router prompt.
Explanation: xxx.xxx.xxx.xxx. is the network address of the destination network and yyy.yyy.yyy.yyy is the subnet mask of the destination network. zzz.zzz.zzz.zzz is the IP address of the direct neighbor interface.

Step 10 - Exit the router global configuration mode.

Task: Enter exit at the router prompt.
Explanation: The router will exit the global configuration mode.

          7. What does the router prompt look like?          

 

Step 11 - Show the running configuration.

Task: Enter show running-config at the router prompt.
Explanation: The router will show the active configuration file.

          8. Was there an IP route with the static route you configured in the active configuration file?

 

Step 12 - Copy the active configuration to the backup configuration.

Task: Enter copy running-config startup-config at the router prompt.
Explanation: This command will permanently write the configuration change to memory.

Step 13 - Test the static route with the ping command.

Task: Enter ping xxx.xxx.xxx.xxx at the router prompt.
Explanation:
xxx.xxx.xxx.xxx. is the neighboring router to which you setup a static route.

          9. Was the neighboring router interface reachable?        

 

Step 14 - Exit the router.

 

Content

 

Lab 12.3.5 Rip routing

Estimated time: 45 min.

Objectives:

  • Configure RIP as your Routing Protocol

Background:

In this lab you will configure RIP as the routing protocol. RIP is a distance-vector routing protocol. Hop count is used as the metric for path selection and has a maximum allowable hop count of 15. RIP broadcasts routing updates consisting of its routing table to its neighbors every 30 seconds by default. RIP is a standard protocol which is appropriate for relatively small homogeneous networks.

Tools / Preparation:

Prior to starting the lab the teacher will have to login to each router and delete all router RIP and static route entries from all of the routers. You will need to connect a PC workstation (with the HyperTerminal program loaded) to a router using the router's console interface with a roll-over (console) cable. All lab work is done through the HyperTerminal program that is configured to connect to the router. You may want to review Chapter 18 in the Cisco Networking Academy First-Year Companion Guide and review Semester 1 on-line chapter 12 prior to starting this lab. Work individually or in teams. Be familiar with the following commands:

  • Enable 
  • Show IP route
  • Show startup-config 
  • Configure terminal 
  • Network 
  • Show running-config
  • Copy
  • Show IP protocols
  • Router RIP

Resources Required:

  • PC with monitor, keyboard, mouse, power cords, etc. 
  • Windows operating system (Win 95, 98, NT or 2000) installed on PC 
  • HyperTerminal program configured for router console connection 
  • PC connected to the router console port with a roll-over cable 

Websites Sites Required:       

Notes:

 


Step 1 – Login to the router.

Explanation: Connect to the router and login.  Enter the password cisco if prompted.

Step 2 - Test layer 3 connectivity. 

Task: Enter ping xxx.xxx.xxx.xxx 
Explanation: Ping all interfaces on your router and direct neighboring routers.

          1. Did all interfaces respond with a successful ping? 

            

Step 3 - View the routing table. 

Task: Enter show IP route at the router prompt. 
Explanation:
The router will respond with its routing table.

          2. Is there any routing protocol defined?

           

Step 4 - Enter privileged mode. 

Task:   
         a. Enter
enable at the command prompt.   
         b. Enter the password of class 
Explanation: You use the
enable command to enter privileged EXEC mode.

Step 5 - Show information about the active configuration file. 

Task: Enter show running-config at the router prompt. 
Explanation:
The router will display information on the active configuration file.

          3. Are there any static routes defined?

           

Step 6 - Enter global configuration mode.

Task: Enter configure terminal at the router prompt. 
Explanation:
To configure the router you must enter the global configuration mode. Notice how the router prompt has changed after this command.

          4. What does the router prompt look like?

           

Step 7 - Enable RIP as your routing protocol. 

Task: Enter router RIP command at the router prompt. 
Explanation: This will enable RIP on the router.

          5. What changed in the router prompt?

           

Step 8 - Enable RIP routing on a particular IP network.

Task: Enter network xxx.xxx.xxx.xxx at the router prompt.
Explanation: xxx.xxx.xxx.xxx is the network address on which you want to enable RIP on.

Step 9 - Enable RIP routing on a particular IP network. 

Task: Repeat step 8 for all the networks directly connected to the router.

Step 10 - Exit router configuration mode. 

Task: Enter exit at the router prompt.
Explanation: The router will exit out of router configuration mode and you will be in global configuration mode.

Step 11 - Exit the router global configuration mode. 

Task: Enter exit at the router prompt. 
Explanation:
The router will exit the global configuration mode.

Step 12 - Show the running configuration. 

Task: Enter show running-config at the router prompt.
Explanation: The router will show the active configuration file.

          6. Is the router RIP protocol turned on and advertising the networks you defined? 

           

Step 13 - Copy the active configuration to the backup configuration.
 

Task: Enter copy running-config startup-config at the router prompt. 
Explanation:
This command will permanently write the configuration change to memory.

           7. What does this command do? 

          
 

Step 14 - View the IP protocols.

Task: Enter show IP protocols at the router prompt. 
Explanation:
The router will display values about routing timers and network information associated with the entire router.

          8. When is the next update due?
 
                

Step 15 - View the routing table. 

Task: Enter show IP route at the router prompt. 
Explanation:
The router will display its routing table.

          9. How many routes were discovered by RIP?

           

Step 16 - Display the status and global parameters.

Task: Enter show IP interface at the router prompt. 
Explanation: The router displays the status and global parameters associated with an interface.

         10. What information did you receive from this command?

           

Step 17 - Display RIP routing updates as they are sent and received.

Task: Enter debug IP RIP at the command prompt.
Explanation: This command allows you to display RIP routing updates as they are sent and received.

          11.What important information did you receive from this command?

           

Step 18 - Turn off debug for RIP.

Task: Enter no debug IP RIP at the router prompt.
Explanation: This command will turn off the debugging for RIP.

Step 19 - Exit the router.

 

Content

 

Lab 12.5.1 Rip convergence challenge

Estimated time: 60 min.

Objectives:

  •  Gain experience and knowledge of routing protocols 
  •  Work with and compare static routes and dynamic routes
  •  Understand the process of convergence

Background:

As a system administrator, there will be times when configuring static routes can be very useful. Static routes are useful for stub networks because there is only one way to get to that network. Security is another reason to use static routes, if you have a network or networks that you don't want the rest of the network to be able to "see" you would not want RIP or other routing protocols sending periodic updates to other routers. With simple networks (few routers) it is sometimes more efficient to use static routes since it conserves bandwidth on WAN links. In this lab you will use static routes for troubleshooting purposes and to see their relationship to dynamic routes and routing protocols.

Tools / Preparation:

Prior to starting this lab you will need to have the equipment for the standard 5-router lab available (routers, hubs, switches, cables, etc.). The routers should be pre-configured by the instructor or lab assistant with the correct IP interface settings etc. RIP should be enabled on all routers. The workstations should also be pre-configured to have the correct IP address settings prior to starting the lab. The routers, hubs and workstations should be labeled.

Work in teams of 3 or more. Before beginning this lab you may want to review Chapter 18 in the Cisco Networking Academy First-Year Companion Guide and Semester 2 On-line Chapter 12.

Resources Required:

  • 5 PC workstations (min.) with Windows operating system and HyperTerminal installed. 
  • 5 Cisco Routers (model 1600 series or 2500 series with IOS 11.2 or later). 
  • 4 Ethernet hubs (10BASE-T with 4 to 8 ports).
  • One Ethernet switch (Cisco Catalyst 1900 or comparable).
  • 5 serial console cables to connect workstation to router console port (with RJ-45 to DB9  converters).
  • 3 Sets of V.35 WAN serial cables (DTE male/ DCE female) to connect from router to router.
  • CAT5 Ethernet Cables wired straight through to connect routers and workstations to hubs and switches.
  • AUI (DB15) to RJ-45 Ethernet transceivers (Quantity depends on the number of routers with AUI ports) to convert router AUI interfaces to 10BASE-T RJ-45.

Websites Sites Required:       

Notes:

Step 1 - Show ip route.

Verify that RIP is enabled and there are no static routes on any of the routers. If there are static routes then remove them with the no IP route xxx.xxx.xxx.xxx command in global config mode.

Step 2 - Enable debugging on Lab-D.

When you use the command debug ip rip you will be able to see all routing updates the router is receiving and sending. Turn on debugging on Lab-D.

Step 3 - Shut down the serial 1 interface on Lab-B.

Shutdown the serial 1 interface on Lab-B with the shutdown command. Watch the debugging information on Lab-D and issue the show ip route command there.

  1. Has the output from the command show ip route changed from when you issued the command in step1?
     
  2. Which networks are inaccessible?
     

Step 4 - Converged network.

After about 5 minutes issue the show ip route command on Lab-D.

  1. Are the networks that were inaccessible in question 2 listed in the output from the show ip route command? 
      

Step 5 - Enter static routes.

Bring Lab-B's serial 1 interface back up. Then enter static routes for all five routers leaving RIP enabled. Issue the show ip route command. Your output from the show ip route command should look like this: Note that there are no R-RIP entries in the routing table.

Lab-D#show ip route 
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR

Gateway of last resort is not set 
C 204.204.7.0/24 is directly connected, Serial1 
S 223.8.151.0/24 [1/0] via 204.204.7.1 
S 201.100.11.0/24 [1/0] via 204.204.7.1 
S 219.17.100.0/24 [1/0] via 204.204.7.1 
S 192.5.5.0/24 [1/0] via 204.204.7.1
S 199.6.13.0/24 [1/0] via 204.204.7.1 
S 205.7.5.0/24 [1/0] via 204.204.7.1 
C 210.93.105.0/24 is directly connected, Ethernet0


Step 6 - Shut down the serial 1 interface on Lab-B.

After you shutdown the serial 1 interface on Lab-B watch the debugging information on Lab-D.   

  1. Do you see any information that would let you know that Lab-B’s serial 1 interface is down?
     
     
                  
  1. Why or why not?
      

Step 7 – Turn off debugging on Lab-D.

Turn off debugging on Lab-D using the undebug all command.

  1. Now that you have a good understanding of static routes, what are the benefits of dynamic routes?









 

Content

 

Lab 12.5.2 Routing loops setup challenge

Estimated time: 30 min.

Objectives:

  • Configure a WAN connection between Lab-A and Lab-E.
  • Demonstrate your ability to configure Serial interfaces.

Background

In this lab you will setup a WAN connection between Lab-A and Lab-E to create alternate paths in the standard router lab setup. Using a set of WAN serial cables, connect Lab-A Serial 1 to Lab-E Serial 0. Remember to set the clock rate on the DCE side of the cable (Lab-E's Serial 0 interface).

Tools / Preparation:

Prior to starting this lab you will need to have the equipment for the standard 5-router lab available (routers, hubs, switches, cables, etc.). The routers should be pre-configured by the instructor or lab assistant with the correct IP interface settings etc. The workstations should also be pre-configured to have the correct IP address settings prior to starting the lab. The routers, hubs and workstations should be labeled.

This lab assumes that the equipment (routers, hubs, workstations, etc.) are assembled and connected in the standard lab topology. Work in teams of 3 or more. You may want to review Chapter 11 in the Cisco Networking Academy First-Year Companion Guide and review Semester 2 On-line Chapter 12.

Resources Required:

  • 5 PC workstations (min.) with Windows operating system and HyperTerminal installed. 
  • 5 Cisco Routers (model 1600 series or 2500 series with IOS 11.2 or later).
  • 4 Ethernet hubs (10BASE-T with 4 to 8 ports). 
  • One Ethernet switch (Cisco Catalyst 1900 or comparable).
  • 5 serial console cables to connect workstation to router console port (with RJ-45 to DB9 converters).
  • 4 Sets of V.35 WAN serial cables (DTE male/ DCE female) to connect from router to router. 
  • CAT5 Ethernet Cables wired straight through to connect routers and workstations to hubs and switches.
  • AUI (DB15) to RJ-45 Ethernet transceivers (Quantity depends on the number of routers with AUI ports)
    to convert router AUI interfaces to 10BASE-T RJ-45.

Websites Sites Required:       

Notes:

 


Step 1 - Verify that all physical connections are correct.

Review the standard semester 2 Lab diagram in the overview section of this lab. You will add a 4th set of V.35 WAN serial cables (DTE male/ DCE female) to connect from router Lab-A interface S1 to router Lab-E interface S0.

Step 2 - Configure Lab-A serial 1 interface.

Login to the router and enter the interface configuration mode. Configure interface serial 1 with the following information (this is a new class C IP address): 
IP address 220.68.33.2 
Subnet Mask 255.255.255.0
Bandwidth of 56

Step 3 - Configure IP host and RIP networks.

After you have finished the configuration for the interface, you will need to add the 220.68.33.0 network with the network command to all 5 routers. Also, add the new IP address to the host table entry for routers Lab-A and Lab-E for name resolution to all routers.

Step 4 - Configure Lab-E serial 0 interface. 

Repeat steps 2 and 3 for Lab-E interface serial 0 with the following information: 
IP address 220.68.33.1 
Subnet Mask 255.255.255.0 
Clock rate 56000 
Bandwidth of 56

Step 5 - Test your setup. 

When you have configured Lab-A's and Lab-E's interfaces, check off the items in the list:

  • Ping from all routers to 220.68.33.1

  • Ping from all routers to 220.68.2 2.2

  • Ping from all Workstations to 220.68.33.1

  • Ping from all Workstations to 220.68.33.2

  • Telnet from Lab-C to 220.68.33.1

  • Telnet from Lab-C to 220.68.33.2

  • Telnet from Workstation to 220.68.33.1

  • Telnet from Workstation to 220.68.33.2  

Step 6 - Troubleshooting. 

If you were not able to finish step 5 then use your troubleshooting skills learned in previous labs to correct the problem. After you have successfully finished step 5 save the running configuration to the startup configuration for all routers. 

 

Content

 

Lab 12.5.3  Preventing routing loops

Estimated time: 45 min.

Objectives:

  • Understand methods of controlling routing loops including hold-down timers, defining a maximum hop count, counting to infinity, poison reverse and split-horizon.
  • Adjust the RIP maximum hop count to control routing loops.

Background:

In the previous challenge lab, you saw how long it took to converge when a link went down. In this lab, your task is to find out how to prevent and control routing loops. The use of hold-down timers, defining a maximum hop count, counting to infinity, poison reverse and split-horizon are all methods of controlling routing loops. You will use the RIP hop count metric to control routing loops in this lab. You should have finished Lab 12.5.2 and have the 4th set of WAN cables connected from Lab-A Serial 1 to Lab-E Serial 0. To learn more about timers look at the worksheet answers "Understanding Timers".

Tools / Preparation:

Prior to starting this lab you will need to have the equipment for the standard 5-router lab available. The routers and workstations should be pre-configured by the instructor or lab assistant with the correct IP settings prior to starting the lab. Before beginning this lab you may want to review Chapters 11 in the Cisco Networking Academy First-Year Companion Guide and Semester 2 On-line Chapter 12.

Resources Required:

  • 5 PC workstations (min.) with Windows operating system and HyperTerminal installed.
  • 5 Cisco Routers (model 1600 series or 2500 series with IOS 11.2 or later). 
  • 4 Ethernet hubs (10BASE-T with 4 to 8 ports).
  • One Ethernet switch (Cisco Catalyst 1900 or comparable).
  • 5 serial console cables to connect workstation to router console port (with RJ-45 to DB9 converters).
  • 4 Sets of V.35 WAN serial cables (DTE male/ DCE female) to connect from router to router.
  • CAT5 Ethernet Cables wired straight through to connect routers and workstations to hubs and switches. 
  • AUI (DB15) to RJ-45 Ethernet transceivers (Quantity depends on the number of routers with AUI ports) to convert router AUI interfaces to 10BASE-T RJ-45.

Websites Sites Required:       

Notes:

 


Step 1 – Turn on debugging.

Working with router Lab-C, turn on debugging with the debug ip rip command.  

Step 2 – Shutdown Lab-A’s Ethernet 0 interface.

Shutdown Lab-A’s Ethernet 0 interface.  From Lab-C, watch the routing information and use the show ip route command to see how many routing updates it takes to flush out Lab-A’s Ethernet 0 network. 

1. How many updates did it take to converge?

Step 3 – Enable Lab-A’s Ethernet 0 interface.

On Lab-A bring Ethernet 0 back up and allow enough time for the network to converge. 

Step 4 – Configure default metric, timers basic and split-horizon on Lab-C.

There are other timers that can be modified to help avoid routing loops.  This lab focuses on hop count.  Change the RIP maximum hop count on router Lab-C to 10 (the default is 16), adjust the routing timers and split horizon using the following commands:

Lab-C#conf t
Lab-C(config)#router rip
Lab-C(config-router)#default-metric 10
Lab-C(config-router)#timers basic 30 60 150 30
Lab-C(config-router)#exit
Lab-C(config)#int s0
Lab-C(config-if)#ip split-horizon
Lab-C(config-if)#int s1
Lab-C(config-if)#ip split-horizon
Lab-C(config-if)#^Z 
Lab-C#

Step 5 - Shutdown Lab-A's Ethernet 0 interface.

Shutdown Lab-A's Ethernet 0 interface. From Lab-C, watch the routing information and use the show ip route command to see how many routing updates it takes to flush out Lab-A's Ethernet 0 network.

2. How many updates did it take to converge?

3. Compare question 1 and 2 and explain why the network converged faster after changing the default  metric, timers and split horizon.

 

Content
Overview
For this lab, your instructor will create/introduce multiple problems in the network.  You have a limited amount of time in which to find and solve the problems so that you can get the entire network up and running.  The tools that you may use for the hardware are in your tool kit.  The tools that you may use for the software (IOS) include ping, trace ip route, telnet, and show arp.  You may use your Engineering Journal and any Web-based resources (including the curriculum) that are available.  As you discover the problems you will document them along with what you did to correct them.

Content
13.1 Troubleshooting the 5-Router Network
13.1.1 The standard configuration
Throughout this entire semester you have been using the same basic configuration for your labs and simulations. For these troubleshooting labs, you can refer to this configuration and imagine what could go wrong with it, in terms of the OSI layers. - Examples of problems in each layer might include:
  • Layer 1 - incorrect cable used
  • Layer 2 - interface not configured for Ethernet
  • Layer 3 - subnet mask is incorrect

 

Content
13.1
Troubleshooting the 5-Router Network
13.1.2
Describe typical layer 1 errors
Layer 1 errors include:
  • broken cables
  • disconnected cables
  • cables connected to the wrong ports
  • intermittent cable connection
  • wrong cables used for the task at hand (must use rollovers, cross-connects, and straight-through cables correctly)
  • transceiver problems
  • DCE cable problems
  • DTE cable problems
  • devices turned off

 

Content
13.1 Troubleshooting the 5-Router Network
13.1.3 Typical layer 2 errors
Layer 2 errors include:
  • improperly configured serial interfaces
  • improperly configured Ethernet interfaces
  • improper encapsulation set (HDLC is default for serial interfaces)
  • improper clockrate settings on serial interfaces

 

Content
13.1 Troubleshooting the 5-Router Network
13.1.4 Typical layer 3 errors
Layer 3 errors include:
  • routing protocol not enabled
  • wrong routing protocol enabled
  • incorrect IP addresses
  • incorrect Subnet Masks
  • incorrect DNS to IP bindings

 

Content
13.1 Troubleshooting the 5-Router Network
13.1.5 Network troubleshooting strategies
The Figure shows one approach to troubleshooting. You may create your own, but there should be some orderly process based on the networking standards that you use.

 

Content
13.1 Troubleshooting the 5-Router Network
13.1.6 Troubleshooting lab on a 5-router network
Lab Activity
  For this lab, your instructor has created/introduced multiple problems in the network. You have a limited amount of time in which to find and solve the problems so that you can get the entire network up and running. The tools that you may use for the hardware are in your tool kit. The tools that you may use for the software (IOS) include ping, trace ip route, telnet, and show arp. You may use your Engineering Journal and any Web-based resources (including the curriculum) that are available.

Content
  Summary
Now that you have completed this chapter, you should be able to troubleshoot:
  • Layer 1 errors
  • Layer 2 errors
  • Layer 3 errors
  • Network Problems

 

Content

 

Lab 13.1.6 Troubleshooting 5-router network - Overview

Estimated time: 30 min.

Objectives:

  • Troubleshoot problems in the 5-router lab network 
  • Document the problems found and corrective action taken 
  • Prepare for Part B of the Final Exam (Router Lab Troubleshooting)

Background:

For this lab, your instructor has created/introduced multiple problems in the network. You have a limited amount of time in which to find and solve the problems so that you can get the entire network up and running.

The tools that you may use for the hardware are in your tool kit.  The tools that you may use for the software (IOS) include ping, trace ip route, telnet, and show arp. You may use your Engineering Journal and any Web-based resources (including the curriculum) that are available. As you discover the problems you will document them along with what you did to correct them.

Tools / Preparation:

Prior to starting this lab you should have the equipment for the standard 5-router lab available. All routers and workstations should be properly configured. You will be asked to leave the room and your instructor or lab assistant will introduce 3 to 5 problems into the lab setup.

Step 1 - Review the physical connections on the standard lab setup.

Review the standard semester 2 lab diagram in the overview section of this lab and check all physical devices, cables and connections. 

Step 2 - Troubleshooting induced network problems.

Basic Problem descriptions:
a) We cannot ping a host on LAB-E's network from a host on LAB-A's network.
b) We cannot telnet from one router to another router's host name

The instructor will induce multiple problems (3 to 5) into the network (see answers section) that can cause these high level symptoms. Your team will have a fixed time period (20 to 30 minutes) to correct the problems. You may use your journals and toolkits to troubleshoot the problems.

Step 3 - Document the problems discovered.

Write down the problems as you encounter them and then indicate what you did to correct them. When you are able to ping from a Lab-A workstation to a Lab-E workstation and telnet from one router to another router's host name, have the instructor verify that you have corrected all problems.

Prob. # Problem discovered Solution Instructor verification
1      
2      
3      
4      
5      

 

Content
Overview
Now that you have a firm understanding of the OSI reference model, LANs, and IP addressing, you are ready to learn about and use the Cisco Internetwork Operating System (IOS). However, before using the IOS, it is important to have firm grasp of WAN and router basics. Therefore, in this chapter, you will learn about WAN devices, technologies, and standards. In addition, you will learn about the function of a router in a WAN. Lastly, you will perform lab activities related to a router lab setup and configuration.

 

2.1 WANs
2.1.1 WANs and devices
A WAN (wide area network) operates at the physical layer and the data link layer of the OSI reference model. It interconnects LANs (local area networks) that are usually separated by large geographic areas. WANs provide for the exchange of data packets/frames between routers/bridges and the LANs they support.

The major characteristics of WANs are:

  • They operate beyond the local LANs geographic scope. They use the services of carriers such as the Regional Bell Operating Companies (RBOCs) and Sprint and MCI. 
  • They use serial connections of various types to access bandwidth over wide-area geographies.
  • By definition, WANs connect devices that are separated by wide geographical areas. Such devices include:
  • routers -- offer many services, including internetworking and WAN interface ports
  • switches -- connect to WAN bandwidth for voice, data, and video communication
  • modems -- interface voice-grade services; channel service units/digital service units (CSU/DSUs) that interface T1/E1 services; and Terminal Adapters/Network Termination 1 (TA/NT1s) that interface Integrated Services Digital Network (ISDN) services
  • communication servers -- concentrate dial-in and dial-out user communication

 

2.1 WANs
2.1.2 WAN standards
WAN physical layer protocols describe how to provide electrical, mechanical, operational, and functional connections for WAN services. These services are most often obtained from WAN service providers such as RBOCs, alternate carriers, post-telephone, and telegraph (PTT) agencies.

WAN data link protocols describe how frames are carried between systems on a single data link. They include protocols designed to operate over dedicated point-to-point, multipoint, and multi-access switched services such as Frame Relay. WAN standards are defined and managed by a number of recognized authorities, including the following agencies:

  • International Telecommunication Union-Telecommunication Standardization Sector (ITU-T), formerly the Consultative Committee for International Telegraph and Telephone (CCITT)
  • International Organization for Standardization (ISO)
  • Internet Engineering Task Force (IETF)
  • Electronic Industries Association (EIA)

WAN standards typically describe both physical layer and data link layer requirements. The WAN physical layer describes the interface between the data terminal equipment (DTE) and the data circuit-terminating equipment (DCE). Typically, the DCE is the service provider and the DTE is the attached device. In this model, the services offered to the DTE are made available through a modem or a CSU/DSU.

Several physical layer standards specify this interface:

  • EIA/TIA-232
  • EIA/TIA-449
  • V.24
  • V.35
  • X.21
  • G.703
  • EIA-530

The common data link encapsulations associated with synchronous serial lines are listed in Figure :

  • High-Level Data Link Control (HDLC) -- an IEEE standard; may not be compatible with different vendors because of the way each vendor has chosen to implement it. HDLC supports both point-to-point and multipoint configurations with minimal overhead 
  • Frame Relay -- uses high-quality digital facilities; uses simplified framing with no error correction mechanisms, which means it can send Layer 2 information much more rapidly than other WAN protocols
  • Point-to-Point Protocol (PPP) -- described by RFC 1661; two standards developed by the IETF; contains a protocol field to identify the network layer protocol
  • Simple Data Link Control Protocol (SDLC) -- an IBM-designed WAN data link protocol for System Network Architecture (SNA) environments; largely being replaced by the more versatile HDLC
  • Serial Line Interface Protocol (SLIP) -- an extremely popular WAN data link protocol for carrying IP packets; being replaced in many applications by the more versatile PPP
  • Link Access Procedure Balanced (LAPB) -- a data link protocol used by X.25; has extensive error checking capabilities
  • Link Access Procedure D-channel (LAPD) -- the WAN data link protocol used for signaling and call setup on an ISDN D-channel. Data transmissions take place on the ISDN B channels
  • Link Access Procedure Frame (LAPF) -- for Frame-Mode Bearer Services; a WAN data link protocol, similar to LAPD, used with frame relay technologies

 

2.1 WANs
2.1.3 WAN technologies
Following is a brief description of the most common WAN technologies. They have been grouped into circuit-switched, cell-switched, dedicated digital, and analog services. For more information click on the Web links that are included.

Circuit-Switched Services
  • POTS (Plain Old Telephone Service) -- not a computer data service, but included for two reasons: (1) many of its technologies are part of the growing data infrastructure, (2) it is a model of an incredibly reliable, easy-to-use, wide-area communications network; typical medium is twisted-pair copper wire
  • Narrowband ISDN (Integrated Services Digital Network) -- a versatile, widespread, historically important technology; was the first all-digital dial-up service; usage varies greatly from country to country; cost is moderate; maximum bandwidth is 128 kbps for the lower cost BRI (Basic Rate Interface) and about 3 Mbps for the PRI (Primary Rate Interface); usage is fairly widespread, though it varies considerably from country to country; typical medium is twisted-pair copper wire
Packet-Switched Services
  • X.25 -- an older technology, but still widely used; has extensive error-checking capabilities from the days when WAN links were more prone to errors, which make it reliable but limits its bandwidth; bandwidth may be as high as 2 Mbps; usage is fairly extensive; cost is moderate; typical medium is twisted-pair copper wire
  • Frame Relay -- a packet-switched version of Narrowband ISDN; has become an extremely popular WAN technology in its own right; more efficient than X.25, but with similar services; maximum bandwidth is 44.736 Mbps; 56kbps and 384kbps are extremely popular in the U.S.; usage is widespread; cost is moderate to low; Typical media include twisted-pair copper wire and optical fiber
Cell-Switched Services
  • ATM (Asynchronous Transfer Mode) -- closely related to broadband ISDN; becoming an increasingly important WAN (and even LAN) technology; uses small, fixed length (53 byte) frames to carry data; maximum bandwidth is currently 622 Mbps, though higher speeds are being developed; typical media are twisted-pair copper wire and optical fiber; usage is widespread and increasing; cost is high
  • SMDS (Switched Multimegabit Data Service) -- closely related to ATM, and typically used in MANs; maximum bandwidth is 44.736 Mbps; typical media are twisted-pair copper wire and optical fiber; usage not very widespread; cost is relatively high
Dedicated Digital Services
  • T1, T3, E1, E3 -- the T series of services in the U.S. and the E series of services in Europe are extremely important WAN technologies; they use time division multiplexing to "slice up" and assign time slots for data transmission; bandwidth is:
  • T1 -- 1.544 Mbps
  • T3 -- 44.736 Mbps
  • E1 -- 2.048 Mbps
  • E3 -- 34.368 Mbps
  • other bandwidths are available
The media used are typical twisted-pair copper wire and optical fiber. Usage is extremely widespread; cost is moderate.
  • xDSL (DSL for Digital Subscriber Line and x for a family of technologies) -- a new and developing WAN technology intended for home use; has a bandwidth which decreases with increasing distance from the phone companies equipment; top speeds of 51.84 Mbps are possible near a phone company office, more common are much lower bandwidths (from 100s of kbps to several Mbps); usage is small but increasing rapidly; cost is moderate and decreasing; x indicates the entire family of DSL technologies, including:
  • HDSL -- high-bit-rate DSL
  • SDSL -- single-line DSL
  • ADSL -- asymmetric DSL
  • VDSL -- very-high-bit-rate DSL
  • RADSL -- rate adaptive DSL
  • SONET (Synchronous Optical Network) -- a family of very high-speed physical layer technologies; designed for optical fiber, but can also run on copper cables; has a series of data rates available with special designations; implemented at different OC (optical carrier) levels ranging from 51.84 Mbps (OC-1) to 9,952 Mbps (OC-192); can achieve these amazing data rates by using wavelength division multiplexing (WDM), in which lasers are tuned to slightly different colors (wavelengths) in order to send huge amounts of data optically; usage is widespread among Internet backbone entities; cost is expensive (not a technology that connects to your house)
Other WAN Services
  • dial-up modems (switched analog) -- limited in speed, but quite versatile; works with existing phone network; maximum bandwidth approx. 56 kbps; cost is low; usage is still very widespread; typical medium is the twisted-pair phone line
  • cable modems (shared analog) -- put data signals on the same cable as television signals; increasing in popularity in regions that have large amounts of existing cable TV coaxial cable (90% of homes in U.S.); maximum bandwidth can be 10 Mbps, though this degrades as more users attach to a given network segment (behaving like an unswitched LAN); cost is relatively low; usage is small but increasing; the medium is coaxial cable.
  • wireless -- no medium is required since the signals are electromagnetic waves; there are a variety of wireless WAN links, two of which are:
  • terrestrial -- bandwidths typically in the 11 Mbps range (e.g. microwave); cost is relatively low; line-of-sight is usually required; usage is moderate
  • satellite -- can serve mobile users (e.g. cellular telephone network) and remote users (too far from any wires or cables); usage is widespread; cost is high

 
Web Links
ISDN
What is X.25?
The Frame Relay Forum
The ATM Forum
Standards Committee T1 Telecommunications

 

2.2 WANs and Routers
2.2.1 Router basics
Computers have four basic components: a CPU, memory, interfaces, and a bus. A router also has these components; therefore, it can be called a computer. However, it is a special purpose computer. Instead of having components that are dedicated to video and audio output devices, keyboard and mouse inputs, and all of the typical easy-to-use GUI software of a modern multimedia computer, the router is dedicated to routing.

Just as computers need operating systems to run software applications, routers need the Internetworking Operating Software (IOS) to run configuration files. These configuration files control the flow of traffic to the routers. Specifically, by using routing protocols to direct routed protocols and routing tables, they make decisions regarding best path for packets. To control these protocols and these decisions, the router must be configured.

You will spend most of this semester learning how to build configuration files from IOS commands in order to get the router to perform the network functions that you desire. While at first glance the router configuration file may look complex, by the end of the semester you will be able to read and completely understand them, as well as write your own configurations.

The router is a computer that selects the best paths and manages the switching of packets between two different networks. Internal configuration components of a router are as follows:

  • RAM/DRAM -- Stores routing tables, ARP cache, fast-switching cache, packet buffering (shared RAM), and packet hold queues. RAM also provides temporary and/or running memory for the router’s configuration file while the router is powered on. RAM content is lost when you power down or restart.
  • NVRAM -- nonvolatile RAM; stores a router’s backup/startup configuration file; content remains when you power down or restart.
  • Flash -- erasable, reprogrammable ROM; holds the operating system image and microcode; allows you to update software without removing and replacing chips on the processor; content remains when you power down or restart; multiple versions of IOS software can be stored in Flash memory
  • ROM -- contains power-on diagnostics, a bootstrap program, and operating system software; software upgrades in ROM require replacing pluggable chips on the CPU
  • interface -- network connection through which packets enter and exit a router; it can be on the motherboard or on a separate interface module

 

2.2 WANs and Routers
2.2.2 The function of a router in a WAN
While routers can be used to segment LAN devices, their major use is as WAN devices. Routers have both LAN and WAN interfaces. In fact, WAN technologies are frequently used to connect routers. They communicate with each other by WAN connections, and make up autonomous systems and the backbone of the Internet. Since routers are the backbone devices of large intranets and of the Internet, they operate at Layer 3 of the OSI model, making decisions based on network addresses (on the Internet, by using the Internet Protocol, or IP). The two main functions of routers are the selection of best paths for incoming data packets, and the switching of packets to the proper outgoing interface. Routers accomplish this by building routing tables and exchanging the network information contained within them with other routers.

You can configure routing tables, but generally they are maintained dynamically by using a routing protocol that exchanges network topology (path) information with other routers.

If, for example, you want any computer (x) to be able to communicate with any other computer (y) anywhere on earth, and with any other computer (z) anywhere in the moon-earth system, you must include a routing feature for information flow, and redundant paths for reliability. Many network design decisions and technologies can be traced to this desire for computers x, y, and z to be able to communicate, or internetwork. However, any internetwork must also include the following:

  • consistent end-to-end addressing
  • addresses that represent network topologies
  • best path selection
  • dynamic routing
  • switching
Lab Activity
  In this lab you will examine a Cisco router to gather information about its physical characteristics and begin to relate Cisco router products to their function. You will determine the model number and features of a specific Cisco router including which interfaces are present and to which cabling and devices they are connected.

 

2.2 WANs and Router
2.2.3 Semester 2 lab topology
The Semester 2 lab topology should be thought of as an enterprise WAN for a medium-sized company with offices around the world. It is not connected to the Internet; it is the company's private network. Also, the topology, as shown, is not redundant -- a failure of any router along the chain will break the network. This network of networks, under a common administration (the company) is called an autonomous system. -    

The Internet is a network of autonomous systems, each of which has routers that typically play one of four roles.

  • internal routers -- internal to one area
  • area border routers -- connect two or more areas
  • backbone routers -- primary paths for traffic that is most often sourced from, and destined for, other networks
  • autonomous system (AS) boundary routers -- communicate with routers in other autonomous systems
While no one entity controls them, the typical entities are:
  • corporations (e.g. MCI Worldcom, Sprint, AT&T, Qwest, UUNet, France Telecom)
  • universities (e.g. University of Illinois, Stanford University)
  • research institutes (e.g. CERN in Switzerland)
  • Internet Service Providers (ISPs)
Although the Semester 2 topology is not a model of the Internet, it is a model of one topology that might represent an autonomous system. The protocol that is routed almost universally is IP; the routing protocol Border Gateway Protocol (BGP) is widely used among the Internet routers.

Router A is in Kuala Lumpur, Router B in San Francisco, Router C in New York City, and Router D and E in Paris. Each of the routers connects to an office or campus LAN. The connections from A-B, B-C, and C-D are leased T1 lines that are attached to the routers' serial interfaces.

Note that each router has an Ethernet LAN attached to it. Typical devices on Ethernet LANs, hosts are shown along with their console cables to allow configuration and display of the routers' contents. Also note that four of the routers have wide-area serial connections between them.
Lab Activity
  This lab will help you develop an understanding of how the Cisco lab routers are set up and connected for the Semester 2 topology. You will examine and document the physical connections between these routers and the other lab hardware components such as hubs, switches, and workstations. 
Lab Activity
  This lab will help you develop an understanding of how the Cisco lab routers and workstations are configured for the Semester 2 topology. You will use IOS commands to examine and document the IP network configurations of each router.

 

Content
Summary

 Now that you have completed this chapter, you should have an understanding of the following:

  • WANs, WAN devices, standards and technologies
  • How routers function in a WAN
Content

 

Lab 2.2.2 Routers  - Overview

Estimated time: 20 min.

Objectives:

  • Determine the model number of a Cisco router and what physical interfaces (ports) it has.

  • Identify the cables attached to the router and what they connect to.

  • Check and/or modify HyperTerminal configuration parameters.

  • Connect to the router as its console using the PC and HyperTerminal program.

  • Determine the IOS version and file name.

  • Determine the CPU type, amount of RAM, NVRAM and Flash memory.

Background:

In this lab you will examine a Cisco router to gather information about its physical characteristics and begin to relate Cisco router products to their function. You will determine the model number and features of a specific Cisco router including which interfaces are present and to which cabling and devices they are connected.

A router is basically a dedicated microcomputer that has a Central Processing Unit (CPU), an operating system (Cisco IOS), RAM, and ROM inside. Routers do not have disk drives, keyboards or monitors. One of the ways to configure or program the router is to connect directly to it with a PC or a dumb terminal. The PC provides a monitor and keyboard for the router which is referred to as its "console". The PC becomes the console which allows you to enter commands and communicate directly with the router. In this lab, you will work with a PC workstation using the Windows HyperTerminal (terminal emulation) program to act as a console to the router and you will configure the proper PC serial port settings in order to connect to and communicate with it.

Tools / Preparation:  

Prior to starting the lab, the teacher or lab assistant will need to check that a router is available and that a PC workstation is connected as a console with HyperTerminal installed and properly configured to access the router. The router should be exposed with all sides clearly visible so that all physical connections and cables can be inspected. Work in teams of 2 or more. Before beginning this lab you may want to review Chapters 3 and 4 in the Cisco Networking Academy First-Year Companion Guide and Semester 2 On-line Chapter 2.

The following resources will be required:

  • Windows PC w/ HyperTerminal installed and configured to access the router
  • Cisco Router (16xx or 25xx model)
  • Console Cable (Roll-Over) connecting the PC serial port to the router console port
  • CAT 5 Ethernet Cable attached to an Ethernet port
  • Ethernet hub or switch
  • WAN Cable attached to a Serial port

Web Site Resources:

Routing basics
General information on routers
2500 series routers
1600 series routers
Terms and acronyms
IP routing protocol IOS command summary

 Notes:

 

 

 

 

 

Step 1 - Examine the router.

1. What is the model number?
 

2. Do you see a console port? (Y/N) 
 

    What port is it connected to on the console terminal (PC workstation)?

3. What type of cable is the console cable, and is it a roll-over, cross-connect or
 straight-through cable?
 

Step 2 - Record all of the interfaces (or port connectors) on the router and, any cable attached.

Explanation: If the port has a cable attached, identify the cable type, connector, and the device attached to the other end. (If a port does not have a cable you should be able to identify the connector type that would be used)

5. Fill in the following table.

Router Interface/ Port Identifier Cable type/ Connector Device and port to which cable is connected 
     
     
     
     
     
     
     
     
     

Step 3 - Review the workstation's 'HyperTerminal' configuration.

Explanation: Click on Start/Programs/Accessories/Communications, and then HyperTerminal. Right Click on the icon that is defined for console access to the Cisco Router and then click Properties. The icon may be named Cisco.ht or something similar. If one does not exist you can create it using the settings shown in the answers to the worksheet. On the Properties screen, click the Phone Number Tab and then click the on the Configure button.

6. Fill in the following table with the information indicated.

Configuration Option Current Setting(s)
COM Port  
Bits per second  
Data bits  
Parity  
Stop Bits  
Flow control  

Step 4 - Display IOS version and other important information related to RAM, NVRAM and Flash memory with the show version command  

Task: Connect to the console port on the router and enter the show version command.
Explanation:
The router will return information about the IOS and memory.

7. What is the IOS version?

8. What is the name of the system image (IOS) file? 


 
9. From where was the router IOS image booted?

10. What type of processor (CPU) and how much RAM does this router have?

11. How many Ethernet interfaces does this router have?

12. How many Serial interfaces?

13. The router backup configuration file is stored in Non-Volatile Random Access Memory (NVRAM). How much NVRAM does this router have?

14. The router operating system (IOS) is stored in Flash memory. How much flash memory does this router have?

   

 

Content

 

Lab 2.2.3.1 Routers  - Overview

Estimated time: 20 min.

Objectives: 

  • Setup the Cisco lab equipment according to the semester 2 topology diagram or analyze the physical connections of an existing lab setup.
  • Document the cabling and connections between devices. 
  • Draw a diagram of your lab equipment setup.

Background:

This lab will help you develop an understanding of how the Cisco lab routers are set up and connected for the Semester 2 topology (see diagram on previous page). You will examine and document the physical connections between these routers and the other lab hardware components such as hubs, switches, and workstations. This lab will utilize the standard setup consisting of 5 routers, 4 hubs, 1 switch, and at least 5 workstations plus all associated cabling and adapters. The next lab 2.2.3.2 will give you an opportunity to document the IP addressing and internal IOS configuration of the routers if they are already configured. If they are not configured, instructions will be provided to configure and test them.

Tools / Preparation:

Prior to starting this lab you will need to have the equipment from the standard 5-router lab available (routers, hubs, switch, etc.). The routers and hubs should be disconnected and stacked. Each cabling type (WAN, LAN, console, power) should be grouped together. If it is not possible to start with equipment disconnected, you should review the steps of the lab with the equipment already connected. This will familiarize you with the physical connections and device interfaces.

The routers may be pre-configured by the instructor or lab assistant with the correct IP interface settings etc. The workstations may also be pre-configured to have the correct IP address settings prior to starting the lab. The routers and workstations should be labeled as indicated in this lab.

Start with the routers, switches, hubs, and cabling disconnected if possible. Your team will need to connect them according to the topology diagram in the overview at the beginning of this lab and then document your findings. This lab requires that you assemble the routers into the standard lab topology or as close as possible depending on the equipment you have. Work in teams of 3 or more. Before beginning this lab you may want to review Chapters 3 and 4 in the Cisco Networking Academy First-Year Companion Guide and Semester 2 On-line Chapter 2.

The following resources will be required: 

  • 5 PC workstations (min.) with Windows operating system and HyperTerminal installed. 
  • 5 Cisco Routers (model 1600 series or 2500 series with IOS 11.2 or later).
  • 4 Ethernet hubs (10BASE-T with 4 to 8 ports).
  • One Ethernet switch (Cisco Catalyst 1900 or comparable).
  • 5 serial console cables to connect workstation to router console port (with RJ-45 to DB9 converters). 
  • 3 Sets of V.35 WAN serial cables (DTE male/ DCE female) to connect from router to router. 
  • CAT5 Ethernet cables wired straight through to connect routers and workstations to hubs and switches. 
  • AUI (DB15) to RJ-45 Ethernet transceivers (Quantity depends on the number of routers with AUI ports) to convert router AUI interfaces to 10BASE-T RJ-45.

Web Site Resources: 

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary
 

Notes:



Step 1 - Router Lab LAN/WAN Preliminary Planning.

When setting up the lab equipment from scratch you will need to give some thought to the questions listed below. Even if you are starting with an existing assembled lab setup, you should review all steps and answer all questions to become more familiar with how the routers are connected. Even though you may not be actually connecting the equipment, you should locate, examine and document the cabling  and physical connections between routers, hubs and workstations.

  • Where should the PC's be placed?
  • Where should the routers be placed?
  • Where should the switch and hubs be placed?
  • How should the Ethernet, serial and power cables be run?
  • How many outlets and power strips will be needed?
  • Which PC connects to which router? 
  • Which PC connects to which hub or switch?
  • Which Router connects to which hub or switch?
  • How should devices and cabling be labeled?

Step 2 - Arrange Lab Equipment.

Your arrangement of the routers and equipment will vary depending on space and physical setup of your lab area. The goal is to group each combination of router/hub/workstation closely together since they can represent separate LANs and geographical locations in the real world. It is easier to see the relationships between equipment with this arrangement. Equipment should be positioned so that all interfaces are facing the same direction and so that cabling and connections can be accessed easily.

A. Table or work surface setup - If you are setting the routers out over tables or desks, place the labeled routers side by side in order from left to right (Lab-A, Lab-B…). Place the switch on top of router Lab-A. Place hub 1 on top of the switch and hubs 2, 3 and 4 on top of routers B, C and D. Place router Lab-D with its hub on top of Lab-E since they are connected to the same LAN. Workstations should be located close to or on the tables for the routers and hubs to which they connect.

B. Single rack setup - If you have a single 19" network equipment rack, mount the first router, Lab-A up high in the rack and mount the switch just above it. Mount the other routers in the rack in sequence from top to bottom with about 4 to 6 inches between each router. Place a hub on top of the switch above router Lab-A and on top of routers B, C and D. Workstations should be spread out around the rack to allow workspace and will be numbered from left to right.

C. Multiple rack setup - If you have multiple racks, put a router and hub in each rack from top to bottom and left to right depending on how many racks you have. Place workstations as close to the routers as possible while still allowing workspace.

Step 3 - Connect Serial WAN Cabling.

Next you will connect serial cables (DCE-DTE) between routers. With this lab setup, the router interface serial 0 (S0) is connected to the DCE cable. DCE refers to Data Circuit-Terminating Equipment (or Data Communications Equipment) connections and represents the clocking end of the synchronous WAN link. The DCE cable has a large female V.35 (34-pin) connector on one end and a DB-60 connector on the other end which attaches to the router serial interface. Interface serial 1 (S1) is connected to the DTE (Data Terminal Equipment) cable. The DTE cable has a large male V.35 connector on one end and a DB60 on the other end which attaches to the router serial interface. Cables are also labeled as DCE or DTE.

1. Examine the cables and connections on the routers and document the connections in the table:

From Router Name Interface To Router Name Interface
       
       

Step 4 - Connect the Router Ethernet Cabling.

For routers that have an AUI (Attachment Unit Interface) Ethernet 0 (E0) or E1 port, you will need an external transceiver which converts the DB15 AUI to an RJ-45 10BASE-T connector. The 2500 series routers usually have an AUI port. The 1600 series has both AUI and RJ-45 ports and you can use the RJ-45 port without the need for the external transceiver. All Ethernet cabling from routers to hubs or switches must be Category 5 (Cat 5) and wired "straight-thru" (pin 1 to pin 1, pin2 to pin 2 etc.). Connect the Ethernet cabling as indicated in the diagram and then label the cabling at each end. Hubs should be numbered Hub 1, Hub 2, etc.

2. Record the router Ethernet interfaces in use and which hub (or switch) they attach to in the table:

From Router Name Router Interface To which Ethernet Device
Lab-A    
Lab-B    
Lab-C    
Lab-D    
Lab-E    
Lab-F     

Step 5 - Connect the Workstation Ethernet Cabling.

Place the PC's at their planned locations and label them (WS-1, WS-2…) from left to right according to the diagram. Run straight-through CAT 5 cables from each PC to where the switch and hubs are located. Connect the Ethernet cabling as indicated and then label the cables at each end depending on what device and interface they connect to. The following table shows the connections for all 10 workstations. Connect at least one workstation to each hub or switch.

3. Indicated which Ethernet device each workstation connects to in the table below:

From Workstation To which Ethernet Device
WS-1  
WS-2  
WS-3  
WS-4  
WS-5  
WS-6  
WS-7  
WS-8  
WS-9  
WS-10  

Step 6 - Connect the Console Workstations to Routers.

Connect one end of the rollover cables from workstations 4, 6, 8, 9, and 10 to the console interface of routers Lab-A, B, C, D and E. Connect the other end of each of the rollover cables to an RJ-45-to-DB-9 serial connector. Connect the serial connector to the serial ports of the 5 workstations. Label the cables at each end.

4. What type of cable is the console cable?          
  

Step 7 - Connect Power Cords to All Devices.

Plug in and turn on all devices. Verify all of them are activated by checking their indicator lights.

5. Are the link lights for the switch, the hubs and the Network Interface Cards (NICs) in the workstations on?


          
Are the OK lights on the back of the routers on?   

Step 8 - Draw your lab diagram.

In the space provided below or in your engineering journal redraw the router lab diagram to match your physical setup. Label all LAN (Ethernet) and WAN (serial) interfaces and cabling.

                                                                                                                 
Content

 

Lab 2.2.3.2 Routers  - Overview

Estimated time: 20 min.

Objectives: 

  • Analyze the routers in an existing lab setup and document the IOS configuration. 

  • Use the show running-config command at each router to determine attached IP Network numbers, Interfaces, IP addresses and subnet mask information for the Local Area Networks (LANs) and Wide Area Networks (WANs) in use. 

  • Use the Control Panel / Network icon or winipcfg.exe utility at each workstation to determine IP address, subnet mask and default gateway settings.

  • Use the Ping command to test the router and workstation connections.

  • Use IOS commands to configure routers to the standard lab setup (optional).

Background: 

This lab will help you develop an understanding of how the Cisco lab routers and workstations are configured for the Semester 2 topology (see diagram on previous page). You will use IOS commands to examine and document the IP network configurations of each router. You will also check the IP configuration of each workstation to ensure that there is full connectivity between all nodes in the lab setup. If the routers are not already configured you may (optionally) use the instructions at the end of the worksheet to configure each router. This will require additional time and probably some assistance from your instructor or a lab assistant since you will not have covered this material in the text, labs or online chapters yet.

Tools / Preparation:  

Prior to starting this lab you will need to have the equipment for the standard 5-router lab available (routers, hubs, switches, cables, etc.). The routers should be pre-configured by the instructor or lab assistant with the correct IP interface settings etc. if possible. The workstations should also be pre-configured to have the correct IP address settings prior to starting the lab. The routers, hubs and workstations should be labeled.

This lab assumes that you have completed the prior lab and that the lab equipment (routers, hub, workstations etc.) are assembled and connected in the standard lab topology. Work in teams of 3 or more. Before beginning this lab you may want to review Chapters 12 and 13 in the Cisco Networking Academy First-Year Companion Guide and Semester 2 On-line Chapter 2.

The following resources will be required: 

  • 5 PC workstations (min.) with Windows operating system and HyperTerminal installed. 
  • 5 Cisco Routers (model 1600 series or 2500 series with IOS 11.2 or later). 
  • 4 Ethernet hubs (10BASE-T with 4 to 8 ports).
  • One Ethernet switch (Cisco Catalyst 1900 or comparable). 
  • 5 serial console cables to connect workstation to router console port (with RJ-45 to DB9 converters). 
  • 3 Sets of V.35 WAN serial cables (DTE male/ DCE female) to connect from router to router.
  • CAT5 Ethernet Cables wired straight-through to connect routers and workstations to hubs and switches.
  • AUI (DB15) to RJ-45 Ethernet transceivers (Quantity depends on the number of routers with AUI ports)  to convert router AUI interfaces to 10BASE-T RJ-45.

Web Site Resources: 

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Notes:

  

  

  

  

  

Step 1 - Verify That All Physical Connections are Correct.

Review the standard semester 2 lab diagram in the overview section of this lab or the diagram you created in the prior lab and check all physical devices, cables and connections. Verify that the routers have been configured correctly (physically and internally) by the instructor or lab assistant.

Step 2 - Examine and Document Router Configurations. (If the routers have not been configured, skip to step 5).

A. Log on to the first router Lab-A. Verify that you have a good console connection from the workstation to the router and start the HyperTerminal program (Start/Programs/Accessories/Communications). Enter the password cisco if prompted to enter user mode. The prompt should be Lab-A> 

B. Enter Privileged Exec mode. Type enable at the router prompt. Enter the password of class if prompted. The prompt should now be Lab-A# C. Gather information about the router. Physically examine each router and make note of the interfaces (E0, S0 etc.) you see. Enter the show running-config command to gather information. The router will respond with the active configuration file currently in RAM. 

1. Fill in the table below with IP interface information for each of the five routers.

Router Name Lab-A Lab-B Lab-C Lab-D Lab-E
Model Number          
Interface EO IP Address          
Interface EO Subnet Mask          
Interface E1 IP Address          
Interface E1 Subnet Mask          
Interface S0 Subnet Mask          
Interface S0 Clock Rate          
Interface S1 IP Address          
Interface S1 Subnet Mask          
Other Intfc(s)          

2. With the information gathered from the show running-config command at router Lab-A, answer the following questions:

a. What is the routing protocol used? 
   

b. What are the networks that are directly connected to the interfaces?
  

c. What is the clock rate of interface S0 on router Lab-A?   
      

d. What is the password for Telnet lines VTY 0 thru 4?
  

Step 3 - Examine and document the workstation configurations. (If the workstations have not been configured, skip to step 6).

A. Verify the workstation IP configuration. 
Click on Start/Settings and select Control Panel. Double-click on the Network icon. Select the TCP/IP protocol and click the Properties button. For each workstation, click the IP Address tab and record the current settings for the IP address, and Subnet mask in the table below. Click the Gateway tab and record the IP address of the default gateway in the table: (should be the IP address of the E0 router interface that the hub is connected to for each workstation). You may also use the winipcfg.exe utility at the DOS command prompt to verify settings at each workstation.

3. Fill in the IP configuration with information obtained from each workstation.

Wkstn # Wkstn. IP addr Wkstn. Submet mask Def. Gateway IP addr.
       
       
       
       
       
       
       
       
       
       

Step 4 - Test the router lab connectivity.

A. Ping from router to router. Begin with router Lab-A and use the console workstation connection to it. Start the HyperTerminal program and ping the S1 interface of router Lab-B. This will verify that the WAN link between Lab-A and Lab-B is OK. Ping the serial interfaces of the other routers. Lab-A> ping 201.100.11.2

4. Was the ping from router Lab-A to Lab-B successful?

   

B. Ping from workstation to router. Begin with a workstation connected to the first hub. Click
Start/Programs/MS-DOS Prompt and ping the S1 interface of router Lab-B. This will verify that the
workstation's IP configuration and the WAN link between Lab-A and Lab-B is OK. Ping the serial
interfaces of the other routers. C:\WINDOWS> ping 201.100.11.2

5. Was the ping from router Lab-A to Lab-B successful? 
   

Step 5 - Configure the routers for the standard lab setup (optional).

If the routers need to be configured, refer to the answers section 6 for the steps necessary. You will need to obtain assistance from your instructor or lab assistant.

Step 6 - Configure the workstations for the standard lab setup (optional).

If the workstations need to be configured, refer to the answers section 7 for the steps necessary. You will need to obtain assistance from your instructor or lab assistant.

Step 7 – The OSI model and associated TCP/IP protocol stack layer.

Task: Fill out the following charts based on your knowledge of the OSI model.
Explanation:
Your understanding of the OSI model will greatly increase your ability to absorb and categorize networking information as you learn it. 

1.  List the 7 layers of the OSI model from the top to the bottom. Give a mnemonic word for each layer that can help you remember it and then list the keywords and phrases that describe the characteristics and function of each.

Layer # Name Mnemonic Key Words and Description of Function
7      
6      
5      
4      
3      
2      
1      

2. List the 7 layers of the OSI model. Indicate the TCI/IP Protocol Stack layer that is associated with each OSI layer. List the encapsulation unit used to describe the data grouping at each layer.

Layer # Name

Encapsulation Unit or Logical Grouping

7    
6    
5    
4    
3    
2    
1    

 

Content
Overview
In this chapter, you will learn about operating a router to ensure delivery of data on a network with routers. You will become familiar with the Cisco CLI (command line interface). You will learn to:
  • login with the user password
  • enter privileged mode with the enable password
  • disable or quit
In addition, you will learn how to use the following advanced help features:
  • command completion and prompting
  • syntax checking
Lastly, you will learn how to use the following advanced editing features:
  • automatic line scrolling
  • cursor controls
  • history buffer with command recall
  • copy and paste, which are available on most computers

Content
3.1 Router User Interface
3.1.1 User and privileged modes
To configure Cisco routers, you must either access the user interface on the router with a terminal or access the router remotely. When accessing a router, you must login to the router before you enter any other commands.

For security purposes, the router has two levels of access to commands
  • user mode --Typical tasks include those that check the router status. In this mode, router configuration changes are not allowed.
  • privileged mode --Typical tasks include those that change the router configuration.
When you first login to a router, you see a user mode prompt. Commands available at this user level are a subset of the commands available at the privileged level. For the most part, these commands allow you to display information without changing router configuration settings.

To access the full set of commands, you must first enable the privileged mode. At the ">" prompt, type "enable". At the "password" prompt, enter the password that has been set with the "enable secret" command. Once you have completed the login steps, the prompt changes to a # (pound sign) because you are now in the privileged mode. From the privileged mode, you can access modes such as the global configuration mode and other specific modes including:
  • interface
  • subinterface
  • line
  • router
  • route-map
  • several additional configuration modes
To logout of the router, type
exit.
Screen output varies with the specific Cisco IOS software level and router configuration.

 

Content
3.1 Router User Interface
3.1.2

User mode command list

Typing a question mark (?) at the user mode prompt or the privileged mode prompt displays a handy list of commonly used commands. Notice the "--More--" at the bottom of the sample display. The screen displays 22 lines at one time. So sometimes you will get the -- More -- prompt at the bottom of the display. It indicates that multiple screens are available as output; that is, more commands follow. Here, or anywhere else in Cisco IOS software, whenever a --More-- prompt appears, you can continue viewing the next available screen by pressing the space bar. To display just the next line, press the Return key (or, on some keyboards, the Enter key). Press any other key to return to the prompt.

Note: Screen output varies, depending on Cisco IOS software level and router configuration.

Content
3.1 Router User Interface
3.1.3 Privileged-mode command list

To access privileged mode, type enable (or as shown in the figure, the abbreviation ena). You will be prompted for a password. If you type a "?" (question mark) at the privileged mode prompt, the screen displays a longer list of commands than it would at the user mode prompt.  -   

Note: Screen output will vary, depending on Cisco IOS software level and router configuration.

 

Content
3.1 Router User Interface
3.1.4 Using router help functions
Suppose you want to set the router clock. If you do not know the command to do so, use the help command to check the syntax for setting the clock. The following exercise illustrates one of the many functions of the help command. Your task is to set the router clock. Assuming that you do not know the command, proceed using the following steps:
  1. Use help to check the syntax for setting the clock. The help output shows that the clock command is required.
  2. Check the syntax for changing the time.
  3. Enter the current time by using hours, minutes, and seconds, as shown. The system indicates that you need to provide additional information to complete the command. The help output in Figure shows that the set keyword is required.
  4. Check the syntax for entering the time and enter the current time using hours, minutes, and seconds. As shown in Figure , the system indicates that you need to provide additional information to complete the command.
  5. Press Ctrl-P (or the up arrow) to repeat the previous command entry automatically. Then add a space and a question mark (?) to reveal the additional arguments. Now you can complete the command entry.
  6. The caret symbol (^) and help response indicate an error. The placement of the caret symbol shows you where the possible problem is located.  To input the correct syntax, re-enter the command up to the point where the caret symbol is located and then enter a question mark (?).
  7. Enter the year, using the correct syntax, and press Return to execute the command.
The user interface provides syntax checking by placing a ^ where the error occurred. The ^ appears at the point in the command string where you have entered an incorrect command, keyword, or argument. The error location indicator and interactive help system enable you to find and correct syntax errors easily.

Note: Screen output varies, depending on Cisco IOS software level and router configuration.

 

Content
3.1 Router User Interface
3.1.5 Using IOS editing commands
The user interface includes an enhanced editing mode that provides a set of editing key functions that allow you to edit a command line as it is being typed. Use the key sequences indicated in Figure to move the cursor around on the command line for corrections or changes. Although enhanced editing mode is automatically enabled with the current software release, you can disable it if you have written scripts that do not interact well while enhanced editing is enabled. To disable enhanced editing mode, type "terminal no editing" at the privileged mode prompt.

The editing command set provides a horizontal scrolling feature for commands that extend beyond a single line on the screen. When the cursor reaches the right margin, the command line shifts 10 spaces to the left. You cannot see the first 10 characters of the line, but you can scroll back and check the syntax at the beginning of the command. To scroll back, press Ctrl-B or the left arrow key repeatedly until you are at the beginning of the command entry, or press Ctrl-A to return directly to the beginning of the line.

In the example shown in Figure , the command entry extends beyond one line. When the cursor first reaches the end of the line, the line is shifted 10 spaces to the left and redisplayed. The dollar sign ($) indicates that the line has been scrolled to the left. Each time the cursor reaches the end of the line, the line is again shifted 10 spaces to the left.

Note: Screen output varies, depending on Cisco IOS software level and router configuration.

 

Content
3.1 Router User Interface
3.1.6 Using IOS command history
The user interface provides a history, or record, of commands that you have entered. This feature is particularly useful for recalling long or complex commands or entries. With the command history feature you can complete the following tasks:
  • Set the command history buffer size.
  • Recall commands.
  • Disable the command history feature.

By default, the command history is enabled and the system records 10 command lines in its history buffer. To change the number of command lines the system records during a terminal session, use the terminal history size or the history size command. The maximum number of commands is 256.

To recall commands in the history buffer, beginning with the most recent command, press Ctrl-P or the up arrow key repeatedly to recall successively older commands. To return to more recent commands in the history buffer, after recalling commands with Ctrl-P or the up arrow, press Ctrl-N or the down arrow key repeatedly to recall successively more recent commands.

When typing commands, as a shortcut, you may enter the unique characters for a command, press the Tab key, and the interface will finish the entry for you. The unique letters identify the command, the Tab key simply acknowledges visually that the router has understood the specific command that you intended.

On most computers you may also have additional select and copy functions available. You can copy a previous command string and then paste or insert it as your current command entry, and press Return. You can use Ctrl-Z to back out of configuration mode.

 

Content
3.2
Using The Router Interface and Interface Modes
3.2.1 Lab: Router user interface
Lab Activity
  This lab will introduce the Cisco Internetwork Operating System (IOS) command line user interface. You will login to the router and use different levels of access to enter commands in “User Mode” and “Privileged Mode”.

 

Content
3.2
Using The Router Interface and Interface Modes
3.2.2 Lab: Router user  interface modes
Lab Activity
  When using router operating systems such as Cisco IOS, you will have to know each of the different user modes a router has and what each one of them is for. Memorizing every command in all of the user modes would be time consuming and pointless. Try to develop an understanding of what commands and functions are available with each of the modes. In this lab, you will work with the topology and the six main modes available with most routers:
  1. User EXEC Mode
  2. Privileged EXEC Mode (also known as Enable Mode)
  3. Global Configuration Mode
  4. Router Configuration Mode
  5. Interface Configuration Mode
  6. Sub-interface Configuration Mode

 

Content
  Summary

You can configure Cisco routers from the user interface that runs on the router console or terminal. For security purposes, Cisco routers have two levels of access to commands: user mode and privileged mode.

Using a user interface to a router, you can:

  • Login with a user password
  • Enter privileged mode with the enable password
  • Disable or quit
You can use advanced help features to perform the following:
  • Command completion and prompting
  • Syntax checking

The user interface includes an enhanced editing mode that provides a set of editing key functions. The user interface provides a history, or record, of commands you have entered.

 

 

Content

 

Lab 3.2.1 Router user interface - Overview

Estimated time: 60 min.

Objectives:

  • Login to a router in both user and privileged modes.
  • Use several basic router commands to determine how the router is configured. 
  • Become familiar with the router HELP facility. 
  • Use the command history and editing features. 
  • Logout of router.

Background:

This lab will introduce the Cisco Internetwork Operating System (IOS) command line user interface. You will login to the router and use different levels of access to enter commands in "User Mode" and "Privileged Mode". You will become familiar with the commands available in each mode (User or Privileged) and use the router HELP facility, history and editing features. The IOS command interface is the most common method of configuring a Cisco router. You will see many commands available, especially in privileged mode. Do not be overwhelmed. As with many things, the 80/20 rule applies. You can do 80% of what you need to do on a daily basis with 20% of the commands available.

Tools / Preparation:

Prior to starting this lab you will need to connect a PC workstation (with the HyperTerminal program loaded) to a router using the router's console interface with a roll-over (console) cable. All lab work is done through the Hyperterminal program that is configured to connect to the router. You may want to review Chapter 12 in the Cisco Networking Academy First-Year Companion Guide and review Semester 1 on-line chapter 3 prior to starting this lab. You will need to be familiar with these commands:  

  • ?
  • enable 
  • logout
  • show ?
  • show running-config
  • exit

Resources Required:     

  • PC with monitor, keyboard, mouse, and power cords, etc. 
  • Windows operating system (Win 95, 98, NT or 2000) installed on PC. 
  • HyperTerminal PE program configured for router console access. 
  • PC connected to the router console port with a roll-over cable.

Websites Site Resources:

Notes:


Step 1
- Login to the router.

Explanation: Connect to the router and login. Enter the password cisco if prompted.

1. What prompt did the router display? What does the prompt symbol mean?

Step 2 - Enter the help command.

Task: Enter the help command by typing (?) at the router prompt.
Explanation:
The router will respond with all of the available commands for User Mode.

2. List eight (8) available commands from the router response. Try to pick ones that might be more commonly used.

. .
. .
. .
. .

Step 3 - Enter enable mode.

Task:   a. From user EXEC mode, enter the privileged mode by using the (enable) command.
           b. Enter the enable password of (
class).
Explanation
: Entering the (
enable) command and using the password (class) allows you privileged mode access to the router.

3. Was "enable" one of the commands available from step 2?

4. What changed in the router prompt display and what does it mean? 

Step 4 - Enter the help command.

Task: Enter the help command by typing (?) at the router prompt.
Explanation:
The router will respond with all of the available commands for Privileged-Mode.

5. List ten (10) available commands from the router response. Try to pick ones that might be more commonly used.

. .
. .
. .
. .
. .


Step 5 - List all
show commands.

Task: Enter show followed by a space then a (?).
Explanation:
The router will respond with the available subcommands for show.

6. Is "running-config" one of the available commands from this user level? 

Step 6 - Look at the running router configuration. 

Task: Enter show running-config at the router prompt.
Explanation:
Using the
show running-config command displays the active configuration file for the router that is stored in RAM.

6a. List 6 key pieces of information you can get from this command:

. .
. .
. .

Step 7 - Continue looking at the configuration. 

Task: When the word "more" appears, hit the space bar.
Explanation:
By pressing the space bar the router will display the next page of information.

7. What happened when you hit the space bar? 

Step 8 - Using the command history. 

Task: Press the up arrow or (Ctrl-P)
Explanation:
Ctrl-P or the "up" arrow commands lets you review your command history.

8. What happened at the router prompt?

Step 9 - Exit the router. 

Task: Enter exit at the router prompt.

 

Content

 

Lab 3.2.2 Router user interface modes - Overview

Estimated time: 20 min.

Objectives:

  • To identify the six basic and two optional router modes
  • To become familiar with the router prompt for each mode
  • Use several commands that will enter specific modes

Background:

When using router operating systems such as Cisco IOS, you will have to know each of the different user modes a router has and what each one of them is for. Memorizing every command in all of the user modes would be time consuming and pointless. Try to develop an understanding of what commands and functions are available with each of the modes. There are six main modes available with most routers:

       1. User EXEC Mode 
       2. Privileged EXEC Mode (also known as Enable Mode) 
       3. Global Configuration Mode
       4. Router Configuration Mode 
       5. Interface Configuration Mode 
       6. Sub-interface Configuration Mode

In this lab you will work with the six most common modes listed above. Two other modes that are used less frequently are RXBoot mode and Setup mode. RXBoot is a maintenance mode that can be used for password recovery. Setup mode presents an interactive prompted dialog at the console that helps a new user create a first-time basic configuration. Both RXBoot and Setup modes will be covered in later labs. 

You can determine which mode you are in by looking at the prompt. Each of the modes will have a different prompt. Depending on which mode you are in, certain commands may or may not be available. You can always type a question mark ? to see what commands you can use. The most common mistake made when working at the command line is to enter a command and get an error because you are in the wrong configuration mode. You need to be familiar with each mode and how to get in and out of each mode.

Tools / Preparation:

Prior to starting the lab you will need to connect a PC (with the HyperTerminal program loaded) to a router using the router's console interface with a roll-over (console) cable. Work individually or in teams. Before beginning this lab you may want to read the Networking Academy First Year Companion Guide, Chapter 12 and 15. You should also review On-line Chapter 3.

Resources Required:     

  • PC with monitor, keyboard, mouse, and power cords, etc. 
  • Windows operating system (Win 95, 98, NT or 2000) installed on PC 
  • HyperTerminal PE program configured for router console access 
  • PC connected to the Router console port with a roll-over cable

Websites Sites Required:       

Routing basics
General information on routers
2500 series routers
IP routing protocol IOS command summary

Notes:

 

 

 

 

 

 

 

For this lab, you and your group should try and discover what each of the modes are and what each of them do. Be sure to take note of what the prompts on the router look like in each of the modes. For example, when in interface config mode, the prompt is: Router(config-if)# (where router is the name of the router you are working with)

1. Match the different router modes with their appropriate prompts (For example: 1-A, 2-B, etc). Fill in the table by writing out the correct prompt selecting from the list of choices provided below:

Mode Description .Mode Prompts
1. User EXEC Mode .
2. Privileged EXEC Mode. .
3. Global configuration mode. .
4. Router configuration mode4  
5. Interface configuration mode  

A. Router# 
B.
Router> 
C.
Router(config-if) #
D.
Router(config-router) # 
E.
Router(config) #

2. Match the different router modes with their functionality. Fill in the table by writing letter of the correct choice provided below:

Mode Description .Mode Prompts
1. User EXEC Mode .
2. Privileged EXEC Mode. .
3. Global configuration mode. .
4. Router configuration mode4  
5. Interface configuration mode  

A. Detailed examination of router, debugging and testing. Remote access. 
B. Setting of IP addresses and subnet masks. 
C. Simple configuration commands. 
D. Limited examination of router. Remote access. 
E. Routing protocols.

3. From the prompt shown below, write a command that will allow you to enter the mode listed:

Desired Mode Current Prompt Command Explanation
Privileged EXEC Mode Router >    
Global Config Mode Router #    
Interface Config Mode Router (config.)#    
Router Config Mode Router  (config.)#    

Router Modes Diagram Exercise

In the space provided or in your Engineering Journal, draw a hierarchical diagram of the various router modes listed in the background section of the lab. At the top of the hierarchy you should have the initial router mode that comes up when you boot up the device. The bottom should have more specific modes. If two or more modes have equal priority choose any order.

                                                                                                                         

Reflection:

In your journal, describe what general function the following modes serve: 

1. Config Interface:

 

2. Enable mode: 

 

Also answer the following: 

1. What did you learn from this lab? 

 

2. Where/when did you have difficulties? 

 

3. How did you overcome them? 

 

4. How can you apply what you learned in this lab toward future labs? 

 

 

Content
Overview

Now that you have an understanding of the router command line interface, it is time to examine the router components that ensure efficient and effective delivery of data on a network. In this chapter, you will learn the correct procedures and commands to access a router, examine and maintain its components, and test its network connectivity.

4.1 Router Components
4.1.1 External router configuration sources
In this section, you will learn about the router components that play a key role in the configuration process. Knowing which components are involved in the configuration process gives you a better understanding of how the router stores and uses your configuration commands. Being aware of the steps that take place during router initialization will help you determine what and where problems may occur when you start up your router.

You can configure a router from many external locations as shown in the Figure, including the following:
  • from the console terminal (a computer connected to the router through a console port) during its installation
  • via modem by using the auxiliary port
  • from Virtual Terminals 0-4, after it has been installed on the network
  • from a TFTP server on the network
Content
4.1 Router Componets
4.1.2 Internal router's configuration components
The internal architecture of the Cisco router supports components that play an important role in the startup process, as shown in the Figure.  Internal router configuration components are as follows:
  • RAM/DRAM -- stores routing tables, ARP cache, fast-switching cache, packet buffering (shared RAM), and packet hold queues; RAM also provides temporary and/or running memory for a router's configuration file while the router is powered; RAM content is lost during a power down or restart
  • NVRAM -- non-volatile RAM stores the router's backup/startup configuration file; NVRAM content is retained during power down or restart
  • Flash -- erasable, reprogrammable ROM that holds the operating system image and microcode; Flash memory enables software updates without removing and replacing processor chips; Flash content is retained during power down or restart; Flash memory can store multiple versions of IOS software
  • ROM -- contains power-on diagnostics, a bootstrap program, and operating system software; software upgrades in ROM require removing and replacing pluggable chips on the CPU
  • Interfaces -- network connections on the motherboard or on separate interface modules, through which packets enter and exit a router
Content
4.1 Router Components
4.1.3
RAM for working storage in the router
RAM is the working storage area for a router. When you turn a router on, the ROM executes a bootstrap program. This program performs some tests, and then loads the Cisco IOS software into memory. The command executive, or EXEC, is one part of the Cisco IOS software. EXEC receives and executes commands you enter for the router.

As shown in the Figure, a router also uses RAM to store an active configuration file and tables of network maps and routing address lists. You can display the configuration file on a remote or console terminal. A saved version of this file is stored in NVRAM. It is accessed and loaded into main memory each time a router initializes. The configuration file contains global, process, and interface information that directly affects the operation of a router and its interface ports.

An operating system image cannot be displayed on a terminal screen. An image is usually executed from the main RAM and loaded from one of several input sources. The operating software is organized into routines that handle the tasks associated with different protocols, such as data movement, table and buffer management, routing updates, and user command execution.

 

Content
4.1 Router Components
4.1.4 Router modes
Whether accessed from the console or by a Telnet session through a TTY port, a router can be placed in several modes. (see Figure) Each mode provides different functions:
  • user EXEC mode -- This is a look-only mode in which the user can view some information about the router, but cannot make changes.
  • privileged EXEC mode -- This mode supports the debugging and testing commands, detailed examination of the router, manipulation of configuration files, and access to configuration modes.
  • setup mode -- This mode presents an interactive prompted dialog at the console that helps the new user create a first-time basic configuration.
  • global configuration mode -- This mode implements powerful one-line commands that perform simple configuration tasks.
  • other configuration modes -- These modes provide more detailed multiple-line configurations.
  • RXBOOT mode -- This is the maintenance mode that you can use, among other things, to recover from lost passwords.
4.2 Router Show Commands
4.2.1 Examining router status by using router status commands
In this section, you will learn basic commands that you can issue to determine the current status of a router. These commands help you obtain vital information you need when monitoring and troubleshooting router operations.

It is important to be able to monitor the health and state of your router at any given time. As shown in the Figure, Cisco routers have a series of commands that allow you to determine whether the router is functionally correct or where problems have occurred. Router status commands and their descriptions are shown below.
  • show version -- displays the configuration of the system hardware, the software version, the names and sources of configuration files, and the boot image
  • show processes -- displays information about the active processes
  • show protocols -- displays the configured protocols; shows the status of all configured Layer 3 protocols
  • show memory -- shows statistics about the router's memory, including memory free pool statistics
  • show stacks --  monitors the stack use of processes and interrupt routines and displays the reason for the last system reboot
  • show buffers -- provides statistics for the buffer pools on the router
  • show flash -- shows information about the Flash memory device
  • show running-config (write term on Cisco IOS Release 10.3 or earlier) -- displays the active configuration file
  • show startup-config (show config on Cisco IOS Release 10.3 or earlier) -- displays the backup configuration file
  • show interfaces -- displays statistics for all interfaces configured on the router

 

4.2 Router Show Commands
4.2.2
The show running-config and show startup-config commands
Among the most used Cisco IOS software EXEC commands are show running-config and show startup-config.   They allow an administrator to see the current running configuration on the router or the startup configuration commands that the router will use on the next restart.

(Note: The commands,
write term and show config, used with Cisco IOS Release 10.3 and earlier, have been replaced with new commands. The commands that have been replaced continue to perform their normal functions in the current release but are no longer documented. Support for these commands will cease in a future release.)

You can recognize an active configuration file by the words current configuration at the top. You can recognize a backup configuration file when you see a message at the top that tells you how much non-volatile memory you have used.

 

4.2 Router Show Commands
4.2.3 The show interfaces, show version, and show protocols commands
The show interfaces command displays configurable parameters and real-time statistics related to all interfaces configured on the router (see Figure ). 

The
show version command displays information about the Cisco IOS software version that is currently running on the router (see Figure ). 

You use the
show protocols command to display the protocols configured on the router. This command shows the global and interface-specific status of any configured Level 3 protocols (for example, IP, DECnet, IPX, and AppleTalk). (see Figure ).

 

4.2 Router Show Commands
4.2.4 Lab: router show commands
Lab Activity
  This lab will help you become familiar with the router show commands. The show commands are the most important information gathering commands available for the router. The show running-config (or "show run") is probably the single most valuable command to help determine the current status of a router because it displays the active configuration file running in RAM. The show startup-config (or "show start") command displays the backup configuration file that is stored in non-volatile or NVRAM. This is the file that will be used to configure the router when it is first started or rebooted with the "reload" command. All of the detailed router interface settings are contained in this file.

The show flash command is used to view the available and the amount used of flash memory. Flash is where the Cisco Internetwork Operating System (IOS) file or image is stored. The show arp command displays the router's IP to MAC to Interface address mapping. The show interface command displays statistics for all interfaces configured on the router. Show protocol command displays global and interface-specific status of configured layer 3 protocols (IP, IPX etc.).

 

4.3 Router's Network Neighbors
4.3.1 Gaining access to other routers by using Cisco Discovery Protocol (CDP)
Cisco Discovery Protocol (CDP) provides a single proprietary command that enables network administrators to access a summary of what the configurations look like on other directly-connected routers. CDP runs over a data link layer that connects lower physical media and upper network layer protocols, as shown in the Figure. Because it operates at this level, CDP devices that support different network layer protocols can learn about each other. (Remember that a data link address is the same as a MAC address.)

When a Cisco device that is running Cisco IOS (Release 10.3 or later) boots up, CDP starts up automatically, which then allows the device to detect neighboring Cisco devices that are also running CDP. Such devices extend beyond those using TCP/IP, and include directly-connected Cisco devices, regardless of which Layer 3 and 4 protocol suite they run.

 

4.3 Router's Network Neighbors
4.3.2 Showing CDP neighbor entries
The primary use of CDP is to discover platforms and protocols on your neighboring devices. Use the show cdp neighbors command to display the CDP updates on the local router.

The Figure displays an example of how CDP delivers its collection of information to a network administrator. Each router that is running CDP exchanges information regarding any protocol entries with its neighbors. The administrator can display the results of this CDP information exchange on a console that is connected to a router configured to run CDP on its interfaces.

The network administrator uses a
show command to display information about the networks directly connected to the router. CDP provides information about each CDP neighbor device. Values include the following:
  • device identifiers -- e.g. the router's configured host name and domain name (if any)
  • address list -- at least one address for SNMP, up to one address for each supported protocol
  • port identifier -- e.g. Ethernet 0, Ethernet 1, and Serial 0
  • capabilities list -- e.g. if the device acts as a source route bridge as well as a router
  • version -- information such as that provided by the local command show version
  • platform -- the device's hardware platform, e.g. Cisco 7000
Notice that the lowest router in the figure is not directly connected to the administrator's console router. To obtain CDP information about this device, the administrator would need to Telnet to a router that is directly connected to this target.

 

4.3 Router's Network Neighbors
4.3.3 A CDP configuration example
CDP begins automatically upon a device's system startup. The CDP function normally starts by default when a Cisco product boots up with Cisco IOS Release 10.3 or later.

Only directly connected neighbors exchange CDP frames. A router caches any information it receives from its CDP neighbors. If a subsequent CDP frame indicates that any of the information about a neighbor has changed, the router discards the older information and replaces it with the new information.
 
Use the command
show cdp interface, as shown in Figure , to display the values of the CDP timers, the interface status, and the encapsulation used by CDP for its advertisement and discovery frame transmission. Default values for timers set the frequency for CDP updates and for aging CDP entries. These timers are set automatically at 60 seconds and 180 seconds, respectively. If the device receives a more recent update, or if this hold-time value expires, the device must discard the CDP entry.

 

4.3 Router's Network Neighbors
4.3.4 Showing CDP entries for a device and CDP neighbors
CDP was designed and implemented as a very simple, low-overhead protocol. A CDP frame can be small yet retrieve a lot of useful information about neighboring routers. You use the command show cdp entry {device name} to display a single cached CDP entry. Notice that the output from this command includes all the Layer 3 addresses present in the neighbor router, Router B. An administrator can view the IP addresses of the targeted CDP neighbor (Router B) with the single command entry on Router A. The hold-time value indicates the amount of elapsed time since the CDP frame arrived with this information. The command includes abbreviated version information about Router B.

You use the command
show cdp neighbors, as shown in Figure , to display the CDP updates received on the local router. Notice that for each local port, the display shows the following:
  • neighbor device ID
  • local port type and number
  • decremental hold-time value, in seconds
  • neighbor device capability code
  • neighbor hardware platform
  • neighbor remote port type and number

To display this information as well as information like that from show cdp entry, you use the optional show cdp neighbors detail

 

4.3 Router's Network Neighbors
4.3.5 Lab: CDP Neighbors
Lab Activity
  In this lab, you will use the show cdp command. Cisco Discovery Protocol (CDP) discovers and shows information about directly connected Cisco devices (routers and switches). CDP is a Cisco proprietary protocol that runs at the data link layer (layer 2) of the OSI model. This allows devices that may be running different network layer 3 protocols such as IP or IPX to learn about each other. CDP begins automatically upon a device's system startup, however if you are using Cisco IOS Release 10.3 or newer version of IOS you must enable it on each of the device's interfaces by using the cdp enable command. Using the command show cdp interface you will gather information CDP uses for its advertisement and discovery frame transmission. Use show cdp neighbors and show cdp neighbors detail to display the CDP updates received on the local router.

 

 

 

 

 

 

4.4 Basic Networking Testing
4.4.1 Testing process that uses the OSI model
The most common problems that occur on IP networks result from errors in the addressing scheme. It is important to test your address configuration before continuing with further configuration steps. Basic testing of a network should proceed in sequence from one OSI reference model layer to the next. Each test presented in this section focuses on network operations at a specific layer of the OSI model. As shown in the Figure, telnet, ping, trace, show ip route, show interfaces and debug are commands that allow you to test your network.

 

 

4.4 Basic Networking Testing
4.4.2 Testing the application layer by using telnet
Another way to learn about a remote router is to connect to it. Telnet, a virtual terminal protocol that is part of the TCP/IP protocol suite, allows connections to be made to hosts. You can set a connection between a router and a connected device. Telnet allows you to verify the application-layer software between source and destination stations. This is the most complete test mechanism available. A router can have up to five simultaneous incoming Telnet sessions. 

Let's begin testing by initially focusing on upper-layer applications. As shown in Figure , the telnet command provides a virtual terminal so administrators can use Telnet operations to connect with other routers running TCP/IP.

With Cisco's implementation of TCP/IP, you do not need to enter the command connect or telnet to establish a Telnet connection. If you prefer, you can just enter the learned host name. To end a Telnet session, use the EXEC commands exit or logout.

The following list shows alternative commands for the operations listed in the figure: 

  • Initiate a session from Denver: 
    Denver> connect paris
    Denver> paris 
    Denver> 131.108.100.152 
  • Resume a session (enter session number or name): 
    Denver>1
    Paris>
  • End a session: 
    Paris> exit

As you have already learned, the Telnet application provides a virtual terminal so that you can connect to other hosts that are running TCP/IP. You can use Telnet to perform a test to determine whether or not you can access a remote router. As is shown in Figure , if you can successfully use Telnet to connect the York router to the Paris router, then you have performed a basic test of the network connection.

If you can remotely access another router through Telnet, then you know that at least one TCP/IP application can reach the remote router. A successful Telnet connection indicates that the upper-layer application (and the services of lower layers, as well) function properly. 

If we can Telnet to one router but not to another router, it is likely that the Telnet failure is caused by specific addressing, naming, or access permission problems. These problems can exist on your router or on the router that failed as a Telnet target. The next step is to try ping, which is covered in this section. This command lets you test end-to-end at the network layer.

Lab Activity
  In this lab, you will work with the telnet (remote terminal) utility to access routers remotely. You will telnet from your “local” router into another “remote” router in order to simulate being at the console on the remote router.

 

4.4 Basic Networking Testing
4.4.3 Testing the network layer using the ping command
As an aid to diagnosing basic network connectivity, many network protocols support an echo protocol. Echo protocols are used to test whether protocol packets are being routed. The ping command sends a packet to the destination host and then waits for a reply packet from that host. Results from this echo protocol can help evaluate the path-to-host reliability, delays over the path, and whether the host can be reached or is functioning.

In the Figure, the ping target 172.16.1.5 responded successfully to all five datagrams sent. The exclamation points (!) indicate each successful echo. If you receive one or more periods (.) instead of exclamations on your display, the application on your router timed out waiting for a given packet echo from the ping target. You can use the ping user EXEC command to diagnose basic network connectivity. The ping uses the ICMP (Internet Control Message Protocol).

Lab Activity
  In this lab you will use ICMP or Internet Control Message Protocol. ICMP will give you the ability to diagnose basic network connectivity. Using ping xxx.xxx.xxx.xxx will send an ICMP packet to the specified host and then wait for a reply packet from that host. You can ping the host name of a router but you must have a static host lookup table in the router or DNS server for name resolution to IP addresses.

 

4.4 Basic Networking Testing
4.4.4
Testing the network layer with the trace command

The trace command is the ideal tool for finding where data is being sent in your network. The trace command is similar to the ping command, except that instead of testing end-to-end connectivity, trace tests each step along the way.  This operation can be performed at either the user or privileged EXEC levels.  

The trace command takes advantage of the error messages generated by routers when a packet exceeds its Time To Live (TTL) value.  The trace command sends several packets and displays the round-trip time for each. The benefit of the trace command is that it tells which router in the path was the last one to be reached. This is called fault isolation.

In this example, we are tracing the path from York to Rome. Along the way the path must go through London and Paris. If one of these routers had been unreachable, you would have seen three asterisks (*) instead of the name of the router. The trace command would continue attempting to reach the next step until you escaped using the Ctrl-Shift-6 escape sequence.
Lab Activity
  In this lab you will use the IOS traceroute command. The traceroute command uses ICMP packets and the error message generated by routers when the packet exceeds its Time To Live (TTL).

 

4.4 Basic Networking Testing
4.4.5 Testing network layer with the show ip route command

The router offers some powerful tools at this point in the search. You can actually look at the routing table - the directions that the router uses to determine how it will direct traffic across the network.

The next basic test also focuses on the network layer. Use the show ip route command to determine whether a routing table entry exists for the target network. The highlight in the graphic shows that Rome (131.108.33.0) is reachable by Paris (131.108.16.2) via the Enternet1 interface.

 

4.4 Basic Networking Testing
4.4.6
Using the show interfaces serial command to test the physical and data link layers
As shown in Figure , the interface has two pieces, physical (hardware) and logical (software):
  • The hardware -- such as cables, connectors, and interfaces -- must make the actual connection between the devices.

  • The software is the messages -- such as keepalive messages, control information, and user information -- that are passed between adjacent devices. This information is data being passed between two connected router interfaces.

When you test the physical and data link, you ask these questions:

  • Is there a Carrier Detect signal?

  • Is the physical link between devices good?

  • Are the keepalive messages being received?

  • Can data packets be sent across the physical link?

One of the most important elements of the show interfaces serial command output is display of the line and data link protocol status. Figure indicates the key summary line to check the status meanings.

The line status in this example is triggered by a Carrier Detect signal, and refers to the physical layer status. However, the line protocol, triggered by keepalive frames, refers to the data link framing.

 

4.4 Basic Networking Testing
4.4.7 The show interfaces and clear counters commands
The router tracks statistics that provide information about the interface. You use the show interfaces command to display the statistics as shown in the figure. The statistics reflect router operation since the last time the counters were cleared, as shown in the top highlighted line in the graphic. This graphic shows that it was two weeks and four days earlier. The bottom set of highlights shows the critical counters. Use the clear counters command to reset the counters to 0. By starting from 0, you get a better picture of the current status of the network.
Lab Activity
  In this lab you will use show interface and clear counters. The router keeps very detailed statistics about data traffic it has sent and received on its interfaces. This is very important in troubleshooting a network problem. The clear counters command resets the counters that are displayed when you issue the show interface command. By clearing the counters you get a clearer picture of the current status of the network.

 

4.4 Basic Networking Testing
4.4.8 Checking real-time traffic with debug
The router includes hardware and software to aid it in tracking down problems, on it, or on other hosts in the network. The debug privileged EXEC command starts the console display of the network events specified in the command parameter. Use the terminal monitor command to forward debug output to your Telnet session terminal.

In this example, data link broadcasts received by the router are displayed. Use the undebug all command (or no debug all) to turn debugging off when you no longer need it. Debugging is really intended for solving problems.

(Note: Be very careful with this tool on a live network. Substantial debugging on a busy network will slow down the network significantly. Do not leave debugging turned on; use it to diagnose a problem, and then turn it off.)

By default, the router sends system error messages and output from the debug EXEC command to the console terminal. Messages can be redirected to a UNIX host or to an internal buffer. The terminal monitor command gives you the capability to redirect these messages to a terminal.

 

4.5 Challenge Lab
4.5.1 Troubleshooting tools challenge
Lab Activity
  As you know, having the topology of a network is extremely useful. It allows a network administrator to know exactly what equipment he or she has in what area (for bandwidth needs), how many devices are on the network and the physical layout of the network.  In this lab you will need to figure out what a topology looks like based on the information you can gather while navigating through the network using IOS commands.

Through the use of show commands, you should be able to see which interfaces are up (using show interface), what devices the router is connected to (using show CDP neighbors) and how the user can get there (using show protocols). With the information received from the show commands, you should be able to remotely access the neighboring routers (using telnet) and through the use of troubleshooting commands (such as ping and trace) you should be able to see which devices are connected. Your final goal is to construct a logical topology drawing of the network by making use of all the above commands without referring to any diagrams ahead of time.

 

Content
  Summary

In this chapter, you learned that:

  • The router is made up of configurable components and has modes for examining, maintaining, and changing the components.
  • show commands are used for examination.
  • You use CDP to show entries about neighbors.
  • You can gain access to other routers by using Telnet.
  • You should test network connectivity layer by layer.
  • Testing commands include telnet, ping, trace, and debug.

 

 

Content

 

Lab 4.2.4 Router show commands

Estimated time: 30 min.

Objectives:

  •  Become familiar with the basic router show commands 
  •  Retrieve the current running configuration of the router in RAM using show running-config 
  •  View the backup configuration file in NVRAM using show startup-config 
  •  View the IOS file information using show flash and show version
  •  View current status of the router interfaces using show interface
  •  View status of any configured layer 3 protocol using show protocol

Background:

This lab will help you become familiar with the router show commands. The show commands are the most important information gathering commands available for the router. The show running-config (or "show run") is probably the single most valuable command to help determine the current status of a router because it displays the active configuration file running in RAM. The show startup-config (or "show start") command displays the backup configuration file that is stored in non-volatile or NVRAM. This is the file that will be used to configure the router when it is first started or rebooted with the "reload" command. All of the detailed router interface settings are contained in this file.

The "show flash" command is used to view the amount available and amount used of flash memory. Flash is where the Cisco Internetwork Operating System (IOS) file or image is stored. The show arp command displays the router's IP to MAC to Interface address mapping. The show interface command displays statistics for all interfaces configured on the router. Show protocol command displays global and interface-specific status of configured layer 3 protocols (IP, IPX, etc.).

Tools / Preparation:

Prior to starting the lab you will need to connect a PC with HyperTerminal to a router using the router's console interface with a roll-over cable. Work individually or in teams. Before beginning this lab you may want to read the Networking Academy First Year Companion Guide, Chapter 13. You should also review On-line Chapter 4. Be familiar with the following show commands: 

  •   Show ? 
  •  Show clock
  •  Show hosts 
  •  Show users 
  •  Show history 
  •  Show arp
  •  Show flash 
  •  Show running-config 
  •  Show startup-config 
  •  Show interface
  •  Show protocol 
  •  Show version

Resources Required:     

  • PC with monitor, keyboard, mouse, and power cords etc. 
  • Windows operating system (Win 95, 98, NT or 2000) installed on PC 
  • HyperTerminal PE program configured for router console access 
  • PC connected to the Router console port with a roll-over cable

Websites Sites Required:    

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Beginning IP for new users 

Notes:

 

 

 

 

 

Step 1 - Log on to router.

Explanation: Connect to the router and login. Enter the password cisco if prompted.

Step 2 - Enter the help command.

Task: Enter the help command by typing (?) at the router prompt. 
Explanation:
The router responds with all commands available in User-Mode.

 
1a. What did the router reply back with ?
   

1b. Are all router commands available at the current prompt?    

2. Is show one of the options available?
   

Step 3 - Display help for the show command.

Task: Enter the show ? command 
Explanation:
The router responds with sub-commands available as part of the show command in user mode. 

3. List three user mode sub-commands available as part of the show command.

Show – sub command

Description

   
   
   

Step 4 - Display IOS version and other important information with the show version command.

Task: Enter the show version command. 
Explanation:
The router will return information about the IOS that is running in RAM.

4. With information from the show version command - Answer the questions below: 

a. What is the IOS version?
 

b. What is the name of the system image (IOS) file? 
 

c. Where was the router IOS image booted from? 
 

d. What type of processor (CPU) and how much RAM does this router have?       

e. How many Ethernet interfaces does this router have? ____ How many Serial interfaces? ____

f. The router backup configuration file is stored in Non-Volatile Random Access Memory (NVRAM).  How much NVRAM does this router have?
 

g. The router operating system (IOS) is stored in Flash memory. How much flash memory does this router have? 
 

h. What is the Configuration register set to?
 

Step 5 - Displaying the routers time and date.

Task: Enter the show clock command. 
Explanation:
The
show clock command will show the current time and date.

5. What information is displayed with show clock?
 

Step 6 - Displaying a cached list of host names and addresses.

Task: Enter show hosts command.
Explanation:
The
show hosts command displays a cached list of hosts and all of their interface IP addresses.

6. What information is displayed with show hosts?


Step 7 - Display users that are connected to the router.

Task: Enter show users command.
Explanation:
The
show users command displayed users that are connected to the router.

7. What information is displayed with show users?


Step 8 - Showing the command buffer.

Task: Enter show history command.
Explanation: The
show history command displays a history of commands that have been entered.

8. What information is displayed with show history?


Step 9 - Enter the privileged mode.

Task: a. From user EXEC mode, enter privileged EXEC mode using the enable command.  
         b.  Enter the enable password of
class
Explanation: Enter the enable mode from the User EXEC mode.

9a. What command did you use to enter privileged mode?



9b. How do you know if you are in privileged-mode?


Step 10 - Enter the help command.

Task: Enter show ? command at the router prompt.
Explanation:
The router responds with the sub-commands available within the show command for Privileged-mode.

10a. What did the router reply back with when show ? was entered at the #?    

10b. How is this output different from the one you got in user mode in step 3?
   

Step 11 - Show the router ARP table.

Task: Enter the show arp command at the router prompt.


Step 12 - Show information about the Flash memory device.

Task: Enter show flash at the router prompt.
Explanation:
The router will respond with information about the flash memory and what IOS file(s) are stored there.

12. Document the following information with show flash.

a. How much flash memory is available and used?


 
b. What is the file that is stored in flash memory?



c. What is the total size in bytes of the flash memory?


Step 13 - Show information about the active configuration file.

Task: Enter show running-config (or show run) at the router prompt.
Explanation: The router will display information on how it is currently configured.

13. What important information is displayed with show run?


Step 14 - Show information about the backup configuration file.

Task: Enter show startup-config (or show start) at the router prompt.
Explanation: The router will display information on the backup configuration file stored in NVRAM.

14. What important information is displayed with show start and where in the router is this information kept?


Step 15 - Display statistics for all interfaces configured on the router.

Task: Enter show interface at the router prompt.
Explanation:
The router shows information about the configured interfaces.

15a. Find the following information for interface Ethernet 0 with show interface:

1. What is MTU?



2. What is Rely?



3. What is Load?

 

4. What is a Runt?



5. What is a Giant?


15b. Find the following information for interface serial0 with Show Interface:

1. What is the IP address and subnet mask?

2. What data link layer encapsulation is being used?



3. What does "Serial0 is up, line protocol is up" mean?


Step 16 - Display the protocols configured on the router.

Task: Enter show protocol at the router prompt.
Explanation:
This command shows the global and interface-specific status of any configured Layer 3 protocols.

16. What important information is displayed?



16b. Enter
exit at the router prompt.

 

Content

 

Lab 4.3.5  CDP neighbors

Estimated time: 30 min.

Objectives: 

  • Use CDP commands to get information about neighboring networks and routers.
  • Display information on how CDP is configured for its advertisement and discovery frame transmission.
  • Display CDP updates received on the local router.

Background:

In this lab you will use the show cdp command. Cisco Discovery Protocol (CDP) discovers and shows information about directly connected Cisco devices (routers and switches). CDP is a Cisco proprietary protocol that runs at the data link layer (layer 2) of the OSI model. This allows devices that may be running different network layer 3 protocols such as IP or IPX to learn about each other. CDP begins automatically upon a device's system startup, however if you are using Cisco IOS Release 10.3 or newer version of IOS you must enable it on each of the device's interfaces by using the cdp enable command. Using the command show cdp interface you will gather information CDP uses for its advertisement and discovery frame transmission. Use show cdp neighbors and show cdp neighbors detail to display the CDP updates received on the local router.

Tools / Preparation:

Prior to starting the lab you will need to connect a PC w/ HyperTerminal to a router using the router's console Interface with a roll-over cable. Work individually or in teams. Before beginning this lab you may want to read the Networking Academy First Year Companion Guide, Chapter 13. You should also review On-line Chapter 4. Be familiar with the following show commands:

  • show interface
  • show cdp
  • show cdp interface
  • show cdp neighbors
  • show cdp neighbors detail

Resources Required: 

  • PC with Windows operating system and HyperTerminal installed 
  • Router connected to the PC with a console roll-over cable
  • At least 3 routers interconnected via Ethernet or WAN simulation cables

Websites Sites Resources:   

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Beginning IP for new users 
    

Notes:

 

 

 

 

 

Step 1 - Log on to router.

Explanation: Connect to the router and login. Enter the password cisco if prompted.

Step 2 - Gather information about the router you logged into by issuing the show interface command. 

Task: Enter show interface command at the router prompt. 
Explanation: The router shows information about the configured interfaces.

1. Document the following information about the router:

a. What is the name of the router? 
 

b. List IP address and subnet mask of the interfaces.

Interface

IP Address Subnet mask
     
     
     
     

c. List operational status of each interface.

Interface Interface Up or Down? (Carrier Detect Signal) Line Protocol Up/Down? (Keep Alives Being received)
     
     
     

Step 3 - Display the values of the CDP timers, the interface status, and encapsulation used. 

Task: Enter show cdp interface command at the router prompt. 
Explanation: The router responds with CDP information on all interfaces that have CDP enabled. 

Global CDP settings can be seen using the show cdp command by itself.

2. How often is the router sending CDP packets? 
 

3. What is the holdtime value? 
 

Step 4 - Display the CDP updates received on the local router. 

Task: Enter show cdp neighbors command at the router prompt. 
Explanation: The router will respond with information about its neighbors that have CDP enabled.

4. Fill in the following table:

Device and Port ID Local Interface Hold Time Capability Platform
         
         
         

Step 5 - Display details about CDP updates received on the local router.

Task: Enter show cdp neighbors detail from the router prompt.
Explanation: The router will display the entry address(es), IOS version, and  the same information as the
show cdp neighbors command.

    5.   Fill in the following table:       

Neighbor device name      
Neighbor device type      
IP address of interface attached to your router      
Port ID of your router that the neighbor is on      
Port ID of neighbor router that your router is on      
IOS version of neighbor router      

Step 6 – Telnet to your neighbor router and issue show cdp neighbor.

Task: 

a.      Telnet to neighboring router by entering telnet (hostname of router or IP address).
b.      Enter the password
cisco.
c.      Enter
show cdp neighbor at the router prompt you have telneted to.


Explanation: The router will respond with information about its neighbors that have CDP enabled. 
NOTE: Perform this step at router lab-b, lab-c, or lab-d and telnet to your two neighbors on either side.

6. Fill in the following tables:  

First neighbor

Device and Port ID Local Interface Hold Time Capability Platform
         
         
          

Second neighbor

Device and Port ID Local Interface Hold Time Capability Platform
         
         
         

 

Content

 

Lab 4.4.2  Remote telnet access

Estimated time: 30 min.

Objectives: 

  • Use the telnet command to remotely access other routers. 
  • Verify that the application layer between source and destination is working properly. 
  • Retrieve information about remote routers using router show commands. 
  • Retrieve CDP information from routers not directly connected to you.

Background:

In this lab you will work with the telnet (remote terminal) utility to access routers remotely. You will telnet from your “local” router into another “remote” router in order to simulate being at the console on the remote router. This procedure will use your router’s Telnet client software and the remote router’s Telnet server software. You can also “telnet” from your workstation as a client into any router connected to your network. In addition, you can telnet into Cisco Ethernet Switches. You can not, however, telnet from a router or a workstation into another Windows client or server since the Windows operating system does not support the Telnet server daemon. A daemon (pronounced demon) is a UNIX term that refers to a program running on a server that accepts requests for services. You can decide whether to allow others to telnet into your router or you may require a password for incoming Telnet sessions. Telnet connections are referred to as line VTY 0 4 in the router configuration file. The router can support up to 5 simultaneous incoming Telnet sessions (0 thru 4).

Telnet is a good troubleshooting tool since it can be used to access remote routers to gather information when there are problems or when configuration changes are necessary. It also tests from the OSI Application layer of the source host down through its Physical layer and then across the network and back up the protocol stack of the destination router. This allows you to verify the Application layer software between source and destination hosts. You will use telnet to access a remote router and use show cdp neighbors to gather information from routers that are not directly connected to you.

Tools / Preparation:

Prior to starting the lab you will need to connect a PC w/ HyperTerminal to a router using the router’s console Interface with a roll-over cable. Work individually or in teams.  Before beginning this lab you may want to read the Networking Academy First Year Companion Guide, Chapter 13.  You should also review On-line Chapter 4. Be familiar with the following commands:

  • telnet ?
  • telnet router-name or IP
  • show CDP neighbors
  • show interface 
  • show protocols
  • enable 
  • show running-config 
  • show startup-config

Resources Required:

  • PC with Windows operating system and HyperTerminal installed 
  • Router connected to the PC with a console roll-over cable
  • At least 3 routers interconnected via Ethernet or WAN simulation cables

Websites Sites Resources:       

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Beginning IP for new users 

Notes: 

 

 

 

 

Step 1 - Log on to the router. 

Task: Connect to the router and login. Enter the password cisco if prompted.

1. What prompt did the router display?
 

Step 2 - Enter the help facility.

Task: Enter telnet ? at the router prompt 
Explanation:
The router will respond with help with the telnet command.

2. What did the router reply with? 
 

Step 3 - Telnet from router to router. 

Task: Enter telnet router-name or IP address at the router prompt to connect to a remote router. 
Explanation:
The router will prompt you for User Access Verification of the router you remotely access. Enter the password cisco

3. What prompt did the router display?
 

Step 4 - Show interfaces. 

Task: Enter show interface at the router prompt. 
Explanation:
The router will respond with information about its interfaces.

4. List the interfaces, their IP address and subnet mask. 

Interface IP Address Subnet mask
     
     
     

Step 5 - Show protocol. 

Task: Enter show protocols at the router prompt. 
Explanation
: This command shows the global and interface-specific status of any configured layer 3 protocols.

5. Fill in the table below with the information that was generated by the router you are remotely  accessing.

Interface Is there a Carrier Detect signal Are the keepalive messages being received?
     
     
     

Step 6 - Enter privileged mode while connected to the remote router with telnet.

Task:
a. Enter
enable at the command prompt. 
b. Enter the password of class  

Explanation: You use the
enable command to enter privileged EXEC mode

 

6. What prompt did the router display? What mode are you in? 



 

Step 7 - Show information about the active configuration file of the remote router. 

Task: Enter show running-config at the remote router prompt. 
Explanation:
The remote router will display information on how it is currently configured.

7. What file are you viewing on the remote router? Where is this file stored?

 

 

Step 8 - Show information about the backup configuration file of the remote router. 

Task: Enter show startup-config at the router prompt.
Explanation: The remote router will display information on the backup configuration file stored in NVRAM.

           8. What file are you viewing on the remote router? Where is this file stored? 

            

            

           9. What information do you see concerning the line VTY connections? 
            

Step 9 - Display the CDP updates received on the local router. 

Task: Enter show cdp neighbors command at the router prompt. 
Explanation:
The router will respond with information about its neighbors that have CDP enabled.

         10. List all device IDs that are connected to the remote router with which you have a telnet session.

   

    

Content

 

Lab 4.4.3  ICMP ping

Estimated time: 30 min.

Objectives: 

  •  Use the ping command to send ICMP Datagrams to target host.
  •  Verify that the network layer between source and destination is working properly.
  •  Retrieve information to evaluate the path-to-host reliability. 
  •  Determine delays over the path and whether the host can be reached or is functioning.

Background:

In this lab you will use ICMP or Internet Control Message Protocol. ICMP will give you the ability to diagnose basic network connectivity. Using ping xxx.xxx.xxx.xxx will send an ICMP packet to the specified host and then wait for a reply packet from that host. You can ping the host name of a router but you must have a static host lookup table in the router or DNS server for name resolution to IP addresses.

Ping is an excellent tool for troubleshooting layers 1 though 3 of the OSI model. If you cannot connect to a host computer (such as a server) but you can ping the server's IP address, then your problem is probably not with the physical cabling connections, the NICs or the routers between you and the server. With this lab, you will also have a chance to see the differences between using the ping command from a router and from a workstation.

Tools / Preparation:

Prior to starting the lab you will need to connect a PC w/ HyperTerminal to a router using the router's console Interface with a roll-over cable. You should have access to the standard 5-router lab if possible. Work individually or in teams. Before beginning this lab you may want to read the Networking Academy First Year Companion Guide, Chapter 13 and you should also review On-line Chapter 4.

Resources Required:

  • PC with Windows operating system and HyperTerminal installed
  • Router connected to the PC with a console roll-over cable
  • At least 3 routers interconnected via Ethernet or WAN simulation cables

Websites Sites Resources:       

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Beginning IP for new users 

Notes: 

 







Step 1 - Log on to router.

Explanation: Connect to the router and login. Enter the password cisco if prompted.

1a. What prompt did the router display?


     
1b What does it mean?

Step 2 - Display a cached list of host names and addresses.

Task: Enter show host at the router prompt.
Explanation:
The router will display information about host to Layer 3 (IP) address mappings, how this information was acquired and the age of the entry.

2. List four (4) host names and the first IP address listed for each one.

Host name IP Address
   
   
   
   

Step 3 - Test layer 3 addressing - Ping from router to router.

Task: Enter ping xxx.xxx.xxx.xxx where xxx.xxx.xxx.xxx is an IP address from one of the other hosts listed above. Repeat with all IP addresses you listed.
Explanation: The router sends an Internet Control Message Protocol (ICMP) packet to verify the hardware connection and network layer address. Since your PC is acting as the console to the router, you are pinging from your router to another router.

3. Were you able to ping all the IP address?

4. List four (4) important pieces of information that you receive back from issuing the ping command.








Step 4 - Examine the output generated by the ping command.

5. Look at the example of the ping command generated by a router.

lab-b#ping 210.93.105.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to 210.93.105.1, timeout is 2 seconds: !!!.!
Success rate is 80 percent (4/5), round-trip min/avg/max = 68/68/168 ms

a. What does the exclamation point (!) indicate?



b. What does the period (.) indicate?



c. What does the
ping command test for?

Step 5 - Access the workstation command prompt.

Task: From a Windows 95/98 or NT workstation click on Start/Programs/MS DOS Command
prompt. This will open a Command Prompt window. 
Explanation: Using the command prompt to ping the routers allows you to test that the TCP/IP stack and default gateway on the workstation are configured and working properly.

Step 6 - Test the workstation default gateway.

Task: Using the command prompt enter ping and the IP address of the workstation default gateway. Default gateway is the nearside router interface IP address. 
Explanation:
By pinging your default gateway you are able to test if you can successfully send packets to and from the router that is directly connected to your LAN.

6. Are you able to ping your default gateway?


(Hint: You may need to check the TCP/IP settings using the Windows Control panel, network icon)

Step 7 - Test layer 3 addressing from a workstation to remote router.

Task: Using the command prompt enter ping and the IP address of a remote router.
Explanation: This will test layer 3 connectivity between your workstation and the remote router.

7. Is the output from the workstation's ping command the same as the output from the ping command from a router?

Step 8 - Test the connections to other remote routers.

Task: Using the command prompt enter ping and the IP address of another remote router.
Explanation: This will test layer 3 connectivity between your workstation and the other remote routers.

8. List the differences between the router's ping command and the workstation ping command.





 

Content

 

Lab 4.4.4 Traceroute command

Estimated time: 30 min.

Objectives: 

  • Use the traceroute Cisco IOS command from source router to destination router.
  • Use the tracert Windows OS command from source workstation to destination router.
  • Use the show ip route command to display the router's routing table.
  • Verify that the network-layer between source, destination and each router along the way is working
    properly. 
  • Retrieve information to evaluate the end-to-end path reliability. 
  • Determine delays at each point over the path and whether the host can be reached.

Background:

In this lab you will use the IOS traceroute command. The traceroute command uses ICMP packets and the error message generated by routers when the packet exceeds its Time To Live (TTL). When you initiate the trace command to a target host the router sends an ICMP echo-request packet with the TTL set to one (1). The first router in the path to the target host receives the ICMP echo-request packet and sets the TTL to zero (0). The first router then sends an ICMP Time-exceeded message back to the source. The source router then sends an ICMP echo-request packet with the TTL set to two (2). The first router receives the ICMP echo-request and sets the TTL to one (1) and (delete enter) sends it to the next router in the path to the target host. The second router receives the ICMP echo-request and sets the TTL to zero (0) then sends an ICMP Ttime-exceeded message back to the source. The source then sends an ICMP echo-request with a TTL set to 3. This cycle continues until an ICMP echo-reply is received from the target host or until a ICMP destination-unreachable message is received. This allows you to determine the last router to be reached in the path to the target host. This is a troubleshooting technique called fault isolation.

Tools / Preparation:

Prior to starting the lab you will need to connect a PC workstation with HyperTerminal to a router using the routers console Interface with a roll-over cable. This lab should be done at the router console station. You may want to review Chapter 13 in the Cisco Networking Academy First-Year Companion Guide and review Semester 2 Online Chapter 4 prior to starting this lab. Work individually or in teams. Be familiar with the following commands:

  • traceroute ip xxx.xxx.xxx.xxx - (Where xxx.xxx.xxx.xxx is the IP address of the host you want to trace). The ip after the command is the default and may be omitted. 
  • traceroute hostname (Where host name is a name that can be resolved to an IP address). traceroute is a  Cisco IOS command.
  • tracert xxx.xxx.xxx.xxx - (Where xxx.xxx.xxx.xxx is the IP address of the host you want to trace). tracert is a  Windows 95/98 or NT command.
  • tracert hostname - (Where host name is a name that can be resolved to an IP address).  
  • show ip route - This will show you the IP routing table - the directions that the router uses to determine how it will direct traffic across the network.

Resources Required:

  •  PC with monitor, keyboard, mouse, and power cords etc. 
  •  Windows operating system (Win 95, 98, NT or 2000) installed on PC
  •  HyperTerminal program 
  •  Access to multiple routers

Websites Sites Resources:       

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Beginning IP for new users 

Notes: 

 







Step 1 - Log on to router.

Explanation: Connect to the router and login. Enter the password cisco if prompted.

1a. What prompt did the router display?


     
1b. What does it mean?

Step 2 - Enter trace (abbreviated form of traceroute). 

Task: Enter trace at the router prompt.

2. What did the router respond with?

Note: After entering the trace command, you need to hit <enter> twice to return to the command line.

Step 3 - Enter trace ? 

Task: Enter trace ? at the router prompt.

3. What did the router respond with? 

Step 4 - Get help with trace ip command. 

Task: Enter trace ip ? at the router prompt.

4. What did the router respond with? 
 

Step 5 - Trace route from end router to end router.

Task: Enter trace ip xxx.xxx.xxx.xxx where xxx.xxx.xxx.xxx is the IP address of the target destination. Note: You will want to do this lab using one of the end routers and trace IP to the other end router. (note: ip is the default) 
Explanation:
Trace command is the ideal tool for finding where data is being sent in your network.

5. List the host name and IP address of the routers that the ICMP packet was routed through.

Host Name IP Address
   
   
   

Step 6 - Trace the route to all other routers on your network.

 Task: Repeat Step 5 with all other routers on your network.

Step 7 - Use tracert from a MS-DOS command prompt.

Task: From the console workstation click on Start/Programs/MS DOS Command Prompt. An MS-DOS Command Prompt window will open up. Enter tracert and the same IP address that you used in step 5.
Explanation:
By using the MS-DOS window you will be using the TCP/IP stack of the workstation to begin the trace to the destination. The first hop will be your default gateway or the near side router interface on the LAN that the workstation is connected to.
 
6a. List the host name and IP address of the router that the ICMP packet was routed through.

Host Name IP Address
   
   
   
   

6b. Why is there one more entry in the output of the tracert command when you trace from the computer command prompt to the target host?


Step 8 – Trace a route over the Internet.

Task: From a Windows 95/98 or NT workstation that has Internet access click on Start/Programs/MS DOS Command Prompt.  An MS-DOS Command Prompt window will open up.
Enter
tracert  www.cisco.com.

7a. What is the IP address of www.cisco.com?

7b. How many hops did it take to get to www.cisco.com? If a packet passes through a router it is considered one (1) hop and the TTL of the packet is decremented by one (1).


Step 9 - View the routing table of the router.

Task: From the router prompt enter show ip route
Explanation:
This will show you the router's routing table.

8. List the IP network number addresses that are directly connect to you. 



 

Content

 

Lab 4.4.7 Show interface & clear counters

Estimated time: 30 min.

Objectives: 

  • Use the show interface command to display statistics for the router's interfaces.
  • Use the clear counters command to clear statistics for the router's interfaces.
     

Background:

In this lab you will use show interface and clear counters. The router keeps very detailed statistics about data traffic it has sent and received on its interfaces. This is very important in troubleshooting a network problem.  The clear counters command resets the counters that are displayed when you issue the show interface command. By clearing the counters you get a clearer picture of the current status of the network.


Tools / Preparation:

Prior to starting the lab you will need to connect a PC workstation with HyperTerminal to a router using the routers console Interface with a roll-over cable. This lab should be done at the router console station. You may want to review Chapter 13 in the Cisco Networking Academy First-Year Companion Guide and review Semester 2 Online curriculum Chapter 4 prior to starting this lab. Work individually or in teams. Be familiar with the following commands:

  • show interface
  • clear counters

Resources Required:

  •  PC with monitor, keyboard, mouse, and power cords etc. 
  •  Windows operating system (Win 95, 98, NT or 2000) installed on PC
  •  HyperTerminal program 
  •  Access to multiple routers

Websites Sites Resources:       

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Beginning IP for new users 

Notes: 

 







Step 1 - Log on to router.

Explanation: Connect to the router and login. Enter the password cisco if prompted.


Step 2 - Enter the
show interface command (abbreviated: sh int)

Task: Enter show interface at the command prompt.
Explanation: The show interface command displays packet statistics which reflect router operation since the last time the counters were cleared.

1.  Fill in the following information for all interfaces in use:  

Interface Ethernet 0 Ethernet 1 Serial 0 Serial 1
Hardware address        
Packet input        
Packet output        
Last clearing of counters        


Step 3
- Enter the
help command.

Task: Enter the help command by typing (?) at the router prompt.
Explanation: The router will respond with all available commands for User-Mode.

2. What is the significance of entering (?) at the command prompt? 
 

Step 4 - Enter Privileged EXEC mode. 

Task: Enter enable at the router prompt. The router will ask you for the enable password enter class.
Explanation: Entering the
enable command and entering the password class allows you privileged mode access to the router.

3. What prompt is the router showing?
 

Step 5 - Get help with the clear command. 

Task: Enter clear ? at the router prompt. 
Explanation: The
clear ? command will display sub commands for clear.

4. Is counters one of the sub commands that is listed?  

5. What is the description of counters?
 

Step 6 - Clear all interface counters. 

Task: Enter clear counters at the router prompt. The router will ask you to confirm with (Y)
Explanation: The
clear command will clear all interface statistics on the router.

Step 7 - Confirm that the counters have been cleared.

Task: Enter show interfaces at the routers command prompt. 
Explanation:
The show interface command displays the statistics, which reflect router operation since the last time the counters were cleared.

6. Have the counters been set to zero (0)?
   

Step 8 - Generate network traffic.

Task: Ping all routers interfaces in the lab network. Do this several times. 
Explanation:
By pinging the interfaces of all routers on the labs network you will generate network traffic. You can use the
Up arrow or CTL-P to retrieve previous commands and change the IP address to the next destination.

Step 9 - Show interface statistics on the router.  

Task: Enter show interface at the router prompt 
Explanation:
The show interface command displays the statistics, which reflect router operation since the last time the counters were cleared.

7. Fill in the following information in the table for all interfaces:

Interface Ethernet 0 Ethernet 1 Serial 0 Serial 1
Hardware address        
Packet input        
Packet output        
Last clearing of counters        

Step 10 - Show interface statistics terminology.

Task: Enter show interface at the router prompt. 
Explanation:
The router shows information about the configured interfaces. Review the terms used for various interfaces and statistics. These can be helpful in troubleshooting.

8. Find the following information for interface Ethernet 0 with show interface:

a. What is MTU?

 

b. What is Rely? 
        


 
c. What is Load?

 

d. What is a Runt?

 

e. What is a Giant?
 
 

9. Find the following information for interface serial 0 with show interface: 
a. What is the IP address and subnet mask?
 

b. What data link layer encapsulation is being used?  

c. What does "Serial0 is up, line protocol is up" mean?
 
 

Content

 

Lab 4.5.1 Troubleshooting tools challenge

Estimated time: 45 min.

Objectives: 

  • Identify what troubleshooting tools (IOS commands) are needed to gather basic information about your network. 
  • Apply what you have learned in past labs to draw a logical diagram of the network.

Background:

As you know, having the topology of a network is extremely useful. It allows a network administrator to know exactly what equipment he or she has in what area (for bandwidth needs), how many devices are on the network and the physical layout of the network. In this lab you will need to figure out what a topology looks like based on the information you can gather while navigating through the network using IOS commands.

Through the use of show commands, you should be able to see which interfaces are up (using show interface), what devices the router is connected to (using show CDP neighbors) and how the user can get there (using show protocols). With the information received from the show commands, you should be able to remotely access the neighboring routers (using telnet) and through the use of troubleshooting commands (such as ping and trace) you should be able to see which devices are connected. Your final goal is to construct a logical topology drawing of the network by making use of all the above commands without referring to any diagrams ahead of time.

Tools / Preparation:

Prior to starting this lab you will need to have the equipment for the standard 5-router lab available (routers, hubs, switches, cables, etc.). The routers should be pre-configured by the instructor or lab assistant with the correct IP interface settings etc. The workstations should also be pre-configured to have the correct IP address settings prior to starting the lab. The routers, hubs and workstations should be labeled. You may also work with a portion of the standard lab setup (3 or more of the routers) connected differently than the standard topology if time permits and try to determine the topology.

This lab assumes that you have completed the prior labs and that the lab equipment (routers, hub, workstations, etc.) are assembled and connected in the standard lab topology. Work in teams of 3 or more. Before beginning this lab you may want to review Chapters 12 and 13 in the Cisco Networking Academy First-Year Companion Guide and Semester 2 On-line Chapters 3 and 4.

Resources Required:

  • 5 PC workstations (min.) with Windows operating system and HyperTerminal installed.

  • 5 Cisco Routers (model 1600 series or 2500 series with IOS 11.2 or later).

  • 4 Ethernet hubs  (10BASE-T with 4 to 8 ports).

  • One Ethernet switch (Cisco Catalyst 1900 or comparable).

  • 5 serial console cables to connect workstation to router console port (with RJ-45 to DB9 converters).

  • 3 Sets of V.35 WAN serial cables (DTE male/ DCE female) to connect from router to router.

  • CAT5 Ethernet Cables wired straight through to connect routers and workstations to hubs and switches.

  • AUI (DB15) to RJ-45 Ethernet transceivers (Quantity depends on the number of routers with AUI ports) to convert router AUI interfaces to 10BASE-T RJ-45.

Websites Sites Resources:       

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Beginning IP for new users 


Step 1 - Gather information about the network.

Use the standard 5-router lab setup or a subset of 3 or more routers. Verify and document the topology of the network that you are working with or have constructed. You will only be able to connect to the console of one of the routers to find out all of the information about the other routers and other devices connected to you.

A. Connect the console to one of the routers in your network. (All information about the physical structure of the network must be obtained from only one console connection.)

1. What command do you use to enter privileged EXEC mode?

 


B. Gather information about the router your console is connected to.

2. What command do you use to gather information about the router you are on?

 
         

C. Gather information about the devices that are connected to your router.

3. What command do you use to gather information about neighboring devices?

 
         

D. Gather information about devices on your network but not directly connected to you.

4. You have gathered information about all interfaces on the router you are working with. You also have the IP address of the devices that are directly connected to the router you are working with. With the information obtained describe how and what commands you will need to use to gather more detailed information about devices not directly connected to your router.









Step 2 - Draw a logical topology of the network.

Using the troubleshooting tools that you have learned from the prior labs in this module, construct a network diagram based on a given topology. In your journal, draw out the logical topology of this network. Include all routers, hubs and switches. Be sure to indicate exactly where there are interfaces. For example, if there is a serial connection from router 1 to router 2, indicate that on the routers. If there is an Ethernet connection to a hub indicate that. Label the diagram with the proper IP addresses and Subnet masks and indicate which end is DCE and which is DTE for each WAN link.

5. Draw the network diagram with the information you have obtained in Step 1.

    

Content
Overview
In the "Router Components" chapter, you learned the correct procedures and commands to access a router, examine and maintain its components, and test its network connectivity. In this chapter, you will learn how to start a router for the first time by using the correct commands and startup sequence to do an initial configuration of a router. In addition, this chapter explains the startup sequence of a router and the setup dialog that the router uses to create an initial configuration file.
5.1 Router Boot Sequence and Setup Mode
5.1.1 Router startup routine
A router initializes by loading the bootstrap, the operating system, and a configuration file. If the router cannot find a configuration file, then it enters setup mode. The router stores, in NVRAM, a backup copy of the new configuration from setup mode.

The goal of the startup routines for Cisco IOS software is to start the router operations. The router must deliver reliable performance in its job of connecting the user networks it was configured to serve. To do this, the startup routines must:

  • Make sure that the router comes up with all its hardware tested.
  • Find and load the Cisco IOS software that the router uses for its operating system.
  • Find and apply the configuration statements about the router, including protocol functions and interface addresses.
When a Cisco router powers up, it performs a power-on self test (POST). During this self test, the router executes diagnostics from ROM on all hardware modules. These diagnostics verify the basic operation of the CPU, memory, and network interface ports. After verifying the hardware functions, the router proceeds with software initialization.
5.1 Router Boot Sequence and Setup Mode
5.1.2 Router startup sequence
After the power-on self test on the router, the following events occur as the router initializes:
  • Step 1 -- The generic bootstrap loader, in ROM, executes on the CPU card. A bootstrap is a simple, preset operation to load instructions that in turn cause other instructions to be loaded into memory, or cause entry into other configuration modes.
  • Step 2 -- The operating system (Cisco IOS) can be found in one of several places. The location is disclosed in the boot field of the configuration register. If the boot field indicates a Flash, or network load, boot system commands in the configuration file indicate the exact location of the image.
  • Step 3 -- The operating system image is loaded. Then, when it is loaded and operational, the operating system locates the hardware and software components and lists the results on the console terminal.
  • Step 4 -- The configuration file saved in NVRAM is loaded into main memory and executed one line at a time. These configuration commands start routing processes, supply addresses for interfaces, set media characteristics, and so on.
  • Step 5 -- If no valid configuration file exists in NVRAM, the operating system executes a question-driven initial configuration routine referred to as the system configuration dialog, also called the setup dialog.
Setup is not intended as the mode for entering complex protocol features in the router. You should use setup to bring up a minimal configuration, then use various configuration-mode commands, rather than setup, for most router configuration tasks.

 

5.1 Router Boot Sequence and Setup Mode
5.1.3 Commands related to router startup
The top two commands in the Figure -- show startup-config and show running-config -- display the backup and active configuration files. The erase startup-config command deletes the backup configuration file in NVRAM. The reload (reboot) command reloads the router, causing it to run through the entire startup process. The last command, setup, is used to enter setup mode from the privileged EXEC prompt.

* Note: The commands show config, write term, and write erase, used with Cisco IOS Release 10.3 and earlier, have been replaced with new commands. The old commands continue to perform their normal functions in the current release, but are no longer documented. Support for these commands will cease in a future release.

 

5.2 System Configuration Dialog
5.2.1 Using the setup command
One of the routines for initial configuration is the setup mode. As you've already learned in this lesson, the main purpose of the setup mode is to bring up, quickly, a minimal configuration for any router that cannot find its configuration from some other source.

For many of the prompts in the system configuration dialog of the setup command facility, default answers appear in square brackets [ ] following the question. Press the Return key to use these defaults. If the system has been previously configured, the defaults that will appear will be the currently configured values. If you are configuring the system for the first time, the factory defaults will be provided. If there is no factory default, as in the case of passwords, nothing is displayed after the question mark [?]. During the setup process, you can press Control+C at any time to terminate the process and start over. Once setup is terminated, all interfaces will be administratively shutdown.

When you complete the configuration process in setup mode, the screen will display the configuration that you have just created. You will then be asked whether you want to use this configuration. If you enter "yes", the configuration will be executed and saved to NVRAM. If you answer "no", the configuration will not be saved and the process will begin again.
If a --
More-- prompt appears, press the space bar to continue.

 

5.2 System Configuration Dialog
5.2.2 Setting up global parameters
After viewing the current interface summary, a prompt will appear on your monitor, indicating that you are to enter the global parameters for your router. These parameters are the configuration values you select.

A prompt appears on your monitor, as illustrated in Figure . It indicates that you are to enter the global parameters that you set for your router. These parameters are the configuration values you decided on.

The first global parameter allows you to set the router host name. This host name will be part of the Cisco IOS prompts for all configuration modes. At initial configuration, the router name default will be displayed between square brackets as [Router].

Use the next global parameters shown in the graphic to set the various passwords used on the router. You must enter an enable password. When you enter a string of password characters for the prompt, "Enter enable secret"; the characters are processed by Cisco proprietary encryption. This enhances the security of the password string. Whenever anyone lists the contents of the router configuration file, this enable password appears as a meaningless string of characters.

Setup recommends, but does not require, that the "enable password" be different from the "enable secret word". The "enable secret word" is a one-way cryptographic secret word that is used instead of the "enable password" when it exists. The "enable password" is used when no "enable secret word" exists. It is also used when using older versions of the IOS. All passwords are case sensitive and can be alphanumeric. 

When you are prompted for parameters for each installed interface, as shown in Figure ,  use the configuration values that you have selected for your router. Whenever you answer yes to a prompt, additional questions may appear regarding the protocol.

 

5.2 System Configuration Dialog
5.2.3 Setting up interface parameters
When you are prompted for parameters for each installed interface, as shown in the Figure, you need to use the configuration values you have determined for your interface to enter the interface parameters at the prompts.
Lab Activity
  In this lab you will use the command setup to enter setup mode. Setup is a Cisco IOS utility (program) that can help get some of the basic router configuration parameters established. Setup is not intended as the mode for entering complex protocol features in the router. Rather the purpose of setup mode is to bring up a minimal configuration for any router that cannot find its configuration from some other source.

 

5.2 System Configuration Dialog
5.2.4 Setting up script review and use
When you complete the configuration process for all installed interfaces on your router, the setup command program will display the configurations that you have created. The setup process will then ask if you want to use this configuration. If you answer yes, the configuration will be executed and saved to NVRAM. If you answer no, the configuration will not be saved, and the process will begin again. There is no default for this prompt; you must answer either yes or no. After you have answered yes to the last question, your system will be ready to use. If you want to modify the configuration you have just established, you must do the configuration manually.

The script tells you to use the configuration mode to change any commands after setup has been used. The script file generated by setup is additive; you can turn features on with setup, but you cannot turn them off. Also, setup does not support many of the advanced features of the router, or features that require a more complex configuration.

 

5.3 Challenge Lab
5.3.1  Router setup lab
Lab Activity
  When you first open up a router and the operating system is loaded, you have to go through the process of initial setup. In this scenario, you have just received a shipment of new routers and you need to setup a basic configuration. You have received a class B IP network address of 156.1.0.0, and you will need to subnet your class B address using 5 bits for you subnets. Use the standard 5-router diagram above to determine which subnetwork numbers and which IP addresses you will use for the 8 networks you will need to define. For this lab, setup all five routers. Be sure to configure the router you are using with the console port.

 

Content
Summary
  • The router initializes by loading a bootstrap, the operating system, and a configuration file.
  • If the router cannot find a configuration file, the router enters setup mode.
  • The router stores a backup copy of the new configuration from setup mode in NVRAM.

 

Content

 

Lab 5.2.3 Router setup command - Overview

Estimated time: 30 min.

Objectives:

  • Become familiar with the router setup mode. 
  • Understand what global parameters can be configured in setup mode.
  • Understand what interface parameters can be configured in setup mode.

Background:

In this lab you will use the command setup to enter setup mode. Setup is a Cisco IOS utility (program) that can help get some of the basic router configuration parameters established. Setup is not intended as the mode for entering complex protocol features in the router. Rather the purpose of setup mode is to bring up a minimal configuration for any router that cannot find its configuration from some other source.

There are two ways to enter setup mode. If the router cannot find its configuration file then it will enter setup mode or setup dialog automatically. The other way to enter setup mode is to enter the setup command at the command line while in privileged mode. The setup dialog prompts you for basic setup options such as which protocols you will be using, the IP address and subnet mask for each interface the router has. The setup dialog provides default values for most of the configurable options. You can either accept these or enter your own. If setup does not provide a prompted entry for specific interface information you will have to manually enter those commands at a later time. With this lab you will run the setup utility but will not save the configuration.

Tools / Preparation:

Prior to starting this lab you should have the equipment for the standard 5-router lab available. The NVRAM of the router you will be configuring should be erased. At the start of this section the instructor or lab assistant should logon to each router in the enable exec mode and issue the erase startup-config command, then issue the reload command. This will force the routers to come up with a blank configuration. The IP configuration for the associated workstation should also be changed so that it is incorrect. The answer section includes examples of the detailed command sets that the students will have to master. The instructor will review your configuration when finished.

Prior to starting this lab you will need to connect a PC workstation (with the HyperTerminal program loaded) to a router using the router's console interface with a roll-over (console) cable. All lab work is done through the Hyperterminal program that is configured to connect to the router. You may want to review Chapter 14 in the Cisco Networking Academy First-Year Companion Guide and review semester 2 online curriculum lesson 5 prior to starting this lab. Work individually or in teams. Be familiar with the following command:

  • setup

Resources Required:     

  • PC connected to the router console port with a roll-over cable 
  • Windows operating system (Win 95, 98, NT or 2000) installed on PC 
  • HyperTerminal PE program configured for router console access 
  • PC connected to the Router console port with a roll-over cable

Websites Sites Required:       

Routing basics 
General information on routers

2500 series routers
 
1600 series routers

Terms and acronyms 

IP routing protocol IOS command summary

Beginning IP for new users 

Notes:

 

 

 

 

 

 

Step 1 - Login to the router. 

Explanation: Connect to the router and login. Enter the password cisco if prompted.

Step 2 - Enter privileged mode

Task: a. Enter enable at the command prompt. 
         b. Enter the password of class.
Explanation:
You use the
enable command to enter privileged EXEC mode.

Step 3 - Enter the help command. 

Task: Enter the help command by typing (?) at the router prompt. 
Explanation:
The router will respond with all available commands for Privileged-Mode.

1. Was setup one of the commands available?

 

Step 4 - Enter setup mode. 

Task: Enter setup at the router prompt. 
Explanation:
Entering the setup command will start setup mode and execute a question-driven initial configuration routine referred to as the system configuration dialog.

Step 5 - Continue with setup dialog. 

Task: Enter yes or press the enter key to continue the setup dialog. 
Explanation:
The router will ask you if you want to continue with configuration dialog.

2. What is the importance of the word in the square brackets?

 

Step 6 - Show the current interface summary. 

Task: Press the enter key or type yes. 
Explanation:
The router will ask "First, would you like to see the current interface summary?" you can press the enter key to accept the default answers.

3. Fill in the following table with the information provided.

Interface

IP-Address OK Method Status Protocol