Computer Networks I Laboratory Exercise 4

Transcription

1 Computer Networks I Laboratory Exercise 4 The lab is divided into two parts where the first part is a basic router configuration. The interfaces and static routes will be configured, and RIP will be used as the routing protocol. In the second part RIPv2 will be configured, to support subnet information in the routing updates.

2 4.1 Basic Router Configuration and Static Routes Objective This lab will focus on the ability to configure a small network with static routes and rip as the routing protocol, how to troubleshoot the network, preventing routing updates through an interface to regulate advertised routes and observing the results. Configuring static routes is a way to allow data transfer between routers without the use of dynamic routing protocols. The following steps are included in this exercise: Configure router interfaces Configure static routes Configure the RIP dynamic routing protocol Observe routing activity using the debug ip rip command. Examine routes using the show ip route command. Prevent routing updates through an interface Use the Passive-interface command and add a default route. Add default routes (gateways) Gather information about routing updates and routing protocols.

3 Step 1 Basic configuration of the routers and workstations 1. To make sure the routers are empty, clear the existing configuration. Router#erase startup-config Erasing the nvram filesystem will remove all files! Continue? [confirm] [OK] Erase of nvram: complete Router#reload 2. Setup a network similar to the one in the diagram and start a HyperTerminal session. Configure the hostnames, console, virtual terminal and enable passwords. 3. Then configure the FastEthernet interfaces. GAD(config)#interface fastethernet 0/0 GAD(config-if)#ip address GAD(config-if)#no shutdown BHM(config)#interface fastethernet 0/0 BHM(config-if)#ip address BHM(config-if)#no shutdown 4. Configure the serial interfaces. GAD(config)#interface serial 0/0/0 GAD(config-if)#ip address GAD(config-if)#clock rate GAD(config-if)#no shutdown BHM(config)#interface serial 0/0/0 BHM(config-if)#ip address BHM(config-if)#no shutdown Save the configurations. 5. Configure the workstations with the proper IP address, subnet mask and default gateway. The configuration for the host connected to the GAD Router is: IP Address IP subnet mask Default gateway The configuration for the host connected to the BHM Router is: IP Address IP subnet mask Default gateway Check connectivity between the workstations using ping. From the workstation attached to the GAD router, ping the workstation attached to the BHM router. C:\>ping

4 Pinging with 32 bytes of data: Request timed out. Request timed out. Request timed out. Request timed out. Ping statistics for : Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms Was the ping successful? Why did the ping fail? 7. Check the interfaces status on both routers with the command show ip interface brief. Are all necessary interfaces up? 8. Using the command show ip route, view the IP routing table for GAD. GAD>show ip route Gateway of last resort is not set C /16 is directly connected, FastEthernet0 C /16 is directly connected, Serial0 Use the command show ip route, view the IP routing table for BHM. BHM>show ip route Gateway of last resort is not set C /16 is directly connected, Serial0 C /16 is directly connected, FastEthernet0 Are all of the routes needed in the routing tables? Based on the output from the show ip route command on the GAD and BHM routers, can a host on network connect to a host on network ? If a route is not in the routing table of the router to which the host is connected, the host cannot reach the destination host. Step 2 Adding static routes 1. To change this situation so that the hosts can ping each other, you have to add static routes or run a routing protocol. In global configuration mode, add a static route on the GAD router to network , and on the BHM router to network GAD(config)#ip route BHM(config)#ip route

5 Why is a static route needed on both routers? 2. Use the command show ip route, view the IP routing table for GAD. GAD>show ip route Gateway of last resort is not set C /16 is directly connected, FastEthernet0 C /16 is directly connected, Serial0 S /16 [1/0] via View the IP routing table for BHM in the same way. Are all of the routes needed in the routing tables? Can a host on network see a host on network ? 3. Check connectivity between workstations using ping. The pings should be successful. Step 3 Configuring RIP 1. Remove the static routes from the routers with the no command: GAD(config)#no ip route BHM(config)#no ip route Check the routing table to make sure the static routes was removed. When the static routes are removed, you should not be able to ping between the hosts. 3. Now, configure RIP as the routing protocol to dynamically exchange routing information. Start with the GAD router. GAD(config)#router rip GAD(config-router)#network GAD(config-router)#network GAD(config-router)#exit GAD(config)#exit Why do you have to add both network and to the rip network statement? Save the configuration. 4. Configure RIP on the BHM router. BHM(config)#router rip BHM(config-router)#network BHM(config-router)#network BHM(config-router)#exit BHM(config)#exit

6 Save the configuration. 5. Verify the connection by pinging from one host to the other. Was the ping successful? 6. From the enable or privileged EXEC mode, examine the routing table entries using the show ip route command on each router. What are the entries in the GAD routing table? What are the entries in the BHM routing table? 7. Enter show ip protocol command on each router. In the configuration, is Routing protocol is RIP displayed?. Step 4 Troubleshooting RIP 1. To make sure that routing updates are being sent, type the command debug ip rip in the privileged EXEC mode prompt. Wait for at least 45 seconds. Was there any output from the debug command? What did the output show? Other debug commands that function with RIP are the following: debug ip rip events debug ip rip trigger debug ip rip database To turn off specific debug commands type the no option, for example no debug ip rip events. To turn off all debug commands type undebug all. 2. Look at the RIP routing tables for each router. Enter show ip route rip. List the routes listed in the routing table? What is the administrative distance? Step 5 Examine the routing table and routing updates 1. To check the routing table for a specific route, from BHM privileged EXEC mode prompt enter show ip route When was the last update? When did BHM receive the last RIP update? Wait five seconds and enter show ip route a second time.

7 What has changed from first time? Wait five seconds and enter show ip route a third time. What has changed from second time? What is the default update time for RIP? 2. Check the ip rip database on the BHM router. Type show ip rip database from the privileged EXEC mode prompt. When was the last update? Wait five second and enter show ip rip database. What has changed from the first time? Wait five seconds and enter show ip rip database. What has changed from the second time? Step 6 Prevent routing updates 1. To stop routing updates from GAD to BHM, enter global configuration mode and then enter router configuration mode by entering the command router rip. Enter the command passiveinterface serial 0/0. This will prevent the GAD router from advertising its routes to the BHM router. GAD(config)#router rip GAD(config-router)#passive-interface serial0/0 2. To confirm this, use the debug ip rip events command on the GAD router. Verify from the output that the router is not sending updates out the interface to the BHM router. Disable the debug output with the no debug all command. 3. Also from the BHM router, issue the show ip route to verify that the route to the GAD LAN has been removed. Attempt to ping from the computers in GAD to the computers in BHM. What is the response? 4. Confirm that the BHM router is still sending update to GAD. To do this, use the debug ip rip events command on the BHM router. Verify from the output that the router is sending updates out the interface to the GAD router. How many routes are being sent? Disable the debug output with the no debug all command. Usually the passive-interface command is used on the FastEthernet interfaces where end devices are connected. There is no need to send routing updates if no routers are connected in the other end. Step 7 Add default routes 1. Since BHM is not getting routing updates, it does not have a route to the outside world. It needs to be provided with a default route. A default route (gateway) is the route that data is sent out if the routing table does not have a specific route to use.

8 From the global configuration mode of BHM, enter: BHM(config)#ip route Verify the default route is in the BHM routing table by issuing the show ip route command. There should be an output similar to the following: BHM#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, * - candidate default U - per-user static route, o - ODR Gateway of last resort is to network C /16 is directly connected, Serial0 C /16 is directly connected, Ethernet0 S* /0 [1/0] via BHM# What is the Gateway of last resort listed? What does the gateway of last resort mean? Be sure to be able to ping from the computers in GAD to the computers in BHM. If not check routing tables and interfaces.

9 4.2 RIP Version 2 and Debugging Objective In this laboratory exercise, you will configure RIP version 2 as the routing protocol and observe the differences between the versions. Use the debug commands to verify proper RIP operations, and analyze the data that is transmitted between the routers. Use the configuration from the previous part of the laboration. Step 1 Examine the debug command Start to examine the debug command on the GAD or BHM router. 1. At the privileged EXEC mode, type debug ip? Which routing protocols can use debug commands? 2. At the privileged EXEC mode type debug ip rip? How many options are available for this command? 3. Use the debug ip rip command on each router to examine the routing table entries. What are the three operations that can take place listed in the rip debug statements? Turn off debugging by typing either no debug ip rip or undebug all. RIPv2 messages include the subnet mask in a field in the routing updates. This allows subnets and their masks to be included in the routing updates, and discontiguous networks can be used without any problems. The RIP protocol summarizes networks at major network boundaries, but the automatic summarization in RIPv2 can be turned off with the command no auto-summary. Step 2 Configure RIP v.2 1. Enable version 2 of the RIP routing protocol on the GAD router only. GAD(config)#router rip GAD(config-router)#version 2 GAD(config-router)#exit 2. Start the debugging on the GAD router again. Does a problem occur now when we have RIP v.2 on the GAD router? What is the problem? 3. Instead of waiting for the routers to time out, type clear ip route * to clear the routing table. Then type show ip route. What has happened to the routing table?

10 Will it be updated to include RIP routes if the debug output says the update is ignored? Turn of the debugging. 4. Start the debug RIP function on the BHM router. Does a problem occur now when RIP v.2 is on the GAD router? What is the problem? 5. Clear the routing table on the BHM router, then take a look at the routing table to see if anything has changed. 6. Enable version 2 of the RIP routing protocol on the BHM router. Use the debug function to examine the packet traffic on the GAD router. Use the command debug ip packet. How many source addresses are used when a RIP update is sent? Why is multiple source addresses used? What is the source address, and why is this address used? 7. Start the RIP database debugging by typing debug ip rip database (not on 2500 series routers) then clear the routing table. Are the old routes in the table deleted? Are new routes added back into the table? What does the last entry in the output debug output say? Turn off the debugging. 8. Now, use the debug function to see routing updates. Type debug ip rip events on the BHM router. What interfaces are the routing updates sent on? How many routes are in the routing updates that are being sent? Once the previous steps are completed, erase the start-up configuration, logoff by typing exit, and turn the router off. Then remove and store the cables.