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20 Jan 2010

Three Router CCNA Static Route Lab

By Bob Marshall

In preparation of your CCNA exam, we want to make sure we cover the various concepts that we could see on your Cisco CCNA exam. So to assist you, below we will discuss one of the more difficult CCNA concepts; the Three Router Static Route Lab. As you progress through your CCNA exam studies, I am sure with repetition you will find this topic becomes easier. So even though it may be a difficult concept and confusing at first, keep at it as no one said getting your Cisco certification would be easy!

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Objective In this lab, you will configure static routes between all three routers. This will allow your routers to route packets so that all routers and all hosts will be able to reach (ping) each other. Once your configuration is complete, you will use basic techniques to test your network's connectivity.

Scenario Three separate classful networks need routing between them and their subnets.

Questions: What are the different classful networks? 1. ________________ 2. ________________ 3. ________________ 4. ________________ 5. ________________ Are there any subnets? If so, what are they? 1. _______________ 2. _______________ 3. _______________ 4. _______________ 5. _______________ Setup Configure the cabling as shown in the network diagram If the routers have a startup-config, erase it and perform a reload of the routers. Important! Configure the routers to include hostnames and the proper interface commands including IP addresses, subnet masks, etc. Each router should be able to ping the interface of the adjacent (neighboring) router and the host on its LAN (Ethernet) interface. Test and troubleshoot as necessary. Use the context sensitive help, previous labs, your books and /or handouts and if your still having problems ask your partner or ask the instructor for assistance. Step 1 - Configuring Static Routes On each router configure a separate and specific static route for each network or subnet. You do not need to configure static routes for the router's directly connected network(s) because like a host, by configuring the IP address and subnet mask on an interface tells the router that it belongs to that network/subnet.

Router1 Router1(config)# ip route 172.16.3.0 255.255.255.0 172.16.2.1 Router1(config)# ip route 192.168.2.0 255.255.255.0 192.168.1.1 Router2 Router2(config)# ip route 172.16.1.0 255.255.255.0 172.16.2.2 Router2(config)# ip route 192.168.1.0 255.255.255.0 172.16.2.2 Router2(config)# ip route 192.168.2.0 255.255.255.0 172.16.2.2 Router3 Router3(config)# ip route 172.16.1.0 255.255.255.0 192.168.1.2 Router3(config)# ip route 172.16.2.0 255.255.255.0 192.168.1.2 Router3(config)# ip route 172.16.3.0 255.255.255.0 192.168.1.2 Verify and Validate: All hosts and all routers should be able to ping every interface in the network. Do a "show running-config" and notice the static routes that you entered. Router# show ip route o What routes to networks do you see? o Which routes are static and which routes are directly connected? o What is the administrative distance for a static route? o What is the administrative distance for a directly connected network? Questions: How does the next-hop-ip-address help with the routing process? _____________________________________________. Does it give the entire route, i.e., subnet mask? _________________ What is it actually doing regarding the routing of the packet? ____________________________________________ How does a packet get from Host 2 to Host 3? ____________________________________________ ____________________________________________ ____________________________________________ Instead of a next-hop-ip-address, what else could you have used? ____________________________________________. What would you need to do if you added new networks or deleted/modified existing networks? ____________________________________________ ____________________________________________ ____________________________________________ Is there any way to summarize several static routes to multiple subnets into a single static route? _____________________________________________ _____________________________________________ _____________________________________________ Outputs Router2#show ip route (Output omitted) Gateway of last resort is not set

172.16.0.0/24 is subnetted, 3 subnets S 172.16.1.0 [1/0] via 172.16.2.2 C 172.16.2.0 is directly connected, Serial0 C 172.16.3.0 is directly connected, Ethernet0 S 192.168.1.0/24 [1/0] via 172.16.2.2 S 192.168.2.0/24 [1/0] via 172.16.2.2

Router1#show ip route (output omitted) Gateway of last resort is not set

172.16.0.0/24 is subnetted, 3 subnets

C 172.16.1.0 is directly connected, Ethernet0 C 172.16.2.0 is directly connected, Serial0 S 172.16.3.0 [1/0] via 172.16.2.1 C 192.168.1.0/24 is directly connected, Serial1 S 192.168.2.0/24 [1/0] via 192.168.1.1

Router3#show ip route (Output omitted) Gateway of last resort is not set

172.16.0.0/24 is subnetted, 3 subnets S 172.16.1.0 [1/0] via 192.168.1.2 S 172.16.2.0 [1/0] via 192.168.1.2 S 172.16.3.0 [1/0] via 192.168.1.2 C 192.168.1.0/24 is directly connected, Serial0 C 192.168.2.0/24 is directly connected, Ethernet0

Step 2 - Configuring Summary Static Routes The configuration of the routers in Step 1 works just great and is a valid way to configure routing on these networks. Earlier, we noticed that the network 172.16.0.0 is divided into several subnets. The Router3 router does not really need separate static routes for each subnet, since all of the 172.16.0.0 subnets can be reached via the same next-hop-ip-address, i.e. Router1. Let's reconfigure the static routes on Router3 so that it only uses a single static route to reach all of the 172.16.0.0 subnets.

Router1 No changes Router2 No changes Router3 First, remove the current static routes: Router3(config)# no ip route 172.16.1.0 255.255.255.0 192.168.1.2 Router3(config)# no ip route 172.16.2.0 255.255.255.0 192.168.1.2 Router3(config)# no ip route 172.16.3.0 255.255.255.0 192.168.1.2 Now, add the new summary static route: Router3(config)# ip route 172.16.0.0 255.255.0.0 192.168.1.2 Verify and Validate: All hosts and all routers should be able to ping every interface in the network. Do a "show running-config" and notice the static routes that you entered. Router3# show ip route o What routes to networks do you now see? Questions: What made this new summary static route work for all subnets? _____________________________________________________ _____________________________________________________ _____________________________________________________ Why is a single summary static route an advantage regarding the size of the routing table? _____________________________________________________ _____________________________________________________ _____________________________________________________ Why is a single summary static route an advantage regarding future changes to the 172.16.0.0 network? _____________________________________________________ _____________________________________________________ _____________________________________________________ Outputs Router3#show ip route (Output omitted)

Gateway of last resort is not set S 172.16.0.0/16 [1/0] via 192.168.1.2 C 192.168.1.0/24 is directly connected, Serial0 C 192.168.2.0/24 is directly connected, Ethernet0

Step 3 - Configuring Default Static Routes Both Step 1 and Step 2 are acceptable ways to configure routing for these networks. We notice that the 172.16.3.0/24 and the 192.168.2.0/24 networks are "stub networks," meaning that there is only one way out (both via Router1).

Router1 No changes Router2 First, remove the current static routes: Router2(config)# no ip route 172.16.1.0 255.255.255.0 172.16.2.2 Router2(config)# no ip route 192.168.1.0 255.255.255.0 172.16.2.2 Router2(config)# no ip route 192.168.2.0 255.255.255.0 172.16.2.2 Now, add the new default static route: Router2(config)# ip route 0.0.0.0 0.0.0.0 172.16.2.2 Router3 First, remove the current static routes: Router3(config)# no ip route 172.16.0.0 255.255.0.0 192.168.1.2 Now, add the new default static route: Router3(config)# ip route 0.0.0.0 0.0.0.0 192.168.1.2 Verify and Validate: All hosts and all routers should be able to ping every interface in the network. Do a "show running-config" and notice the static routes that you entered. Router2# show ip route o What routes to networks do you now see? Router3# show ip route o What routes to networks do you now see? Questions: Do you think static routes are still used even with dynamic routing (RIP, OSPF, etc.)? _______________. Hint: Think about the administrative distance. Do you think default static routes are still used even with dynamic routing (RIP, OSPF, etc.)? _______________. What is the disadvantage of doing this? How would a default static route be properly used in a real world network? (How would a company's network use a default route when connecting to the Internet?) ________________________________________ ________________________________________ ________________________________________ Outputs Router3#show ip route (Output omitted)

Gateway of last resort is 192.168.1.2 to network 0.0.0.0

C 192.168.1.0/24 is directly connected, Serial0 C 192.168.2.0/24 is directly connected, Ethernet0 S* 0.0.0.0/0 [1/0] via 192.168.1.2

Save your current configuration to NVRAM.

End of Lab I hope you found this article to be of use and it helps you prepare for your Cisco CCNA certification. Achieving your CCNA certification is much more than just memorizing Cisco exam material. It is having the real world knowledge to configure your Cisco equipment and be able to methodically troubleshoot Cisco issues. So I encourage you to continue in your studies for your CCNA exam certification.

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