Config VM: Fallback Static Routes

Wendell Odom
By Wendell Odom December 15, 2014 09:10

Fallback static routes play a key role in several types of configurations used in Cisco routers. For #CCNA, fallback static routes is one of those corner topics that don’t get a lot of attention. Today’s Config Museum post gives you a chance to configure some fallback static routes that will be used once you disable OSPF on one router.

You can read more about Fallback static routes in the latest version of the ICND2 Cert Guide’s Appendix B (downloadable from the updates tab). Also, these three other Config Museum labs build around the same topology as this lab, in case you want some more background work:

Problem: Build Fallback Static Routes for LAN Subnets

This lab begins with all the interfaces shown in Figure 1 working, with IPv4 addresses configured, and with OSPF configured and working for all subnets. Your job: configure fallback static routes that will not be used while OSPF continues to work. However, when you disable OSPF on router R3, your fallback static routes should then be used.

The specific rules for this lab are as follows:

  1. For this lab, consider routes to subnet only, just to keep the task more manageable.
  2. OSPF is working correctly on all routers, for all subnets, at the beginning of the lab.
  3. Configure the static routes for this contrived failure case: remove the OSPF configuration on router R3 only.

Figure 1: Router Triangle with IP Subnets


Initial Configuration

While you might be able to configure your static routes based on the information supplied so far, the initial configurations of the three routers can also be helpful. Examples 1, 2, and 3 show the beginning configuration state of the three routers. Note that you can try these commands using the simulator that comes with the AIO VM.

Example 1: R1 Config


Example 2: R2 Config


Example 3: R3 Config


Answers Next Post!

I’ll post the answers in the following post, as usual with these labs.



OSPF Interface Config – Answers (Config Museum)
Answers, Config Museum: Fallback Static Route
Wendell Odom
By Wendell Odom December 15, 2014 09:10
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