In the output for the SVI configuration in Example 21-9, you see three different show command outputs from R1, each of which needs to be looked at individually and together to help you make sure that you have configured the routing protocol correctly. Start by taking a look at the first show command and identify the key parts of the output that can help validate or troubleshoot your configurations. From the show running-config eigrp command , you see the configuration output of what you have configured in particular to EIGRP on this Nexus device. Notice that the EIGRP autonomous system ID of 1 is the same for the router eigrp 1 command as it is for the ip router eigrp 1 subinterface command. This tells you
that you have configured the correct EIGRP process on each interface for the global routing process, which is key to validating that your configuration is correct. You can execute these same commands on each Layer 3 switch to confirm correct configurations are in place.

NOTE

EIGRP uses what is known as an autonomous system ID. This number must match for the routers to form as neighbors. In our example, number 1 is the autonomous system number (between 1 and 65,535), which must be the same on all EIGRP-speaking routers in the network that would like to communicate and share routing information.

The last two show commands, show ip eigrp and show ip eigrp neighbors, enable you to validate or troubleshoot that you have formed neighbor relationships with other Layer 3 switches and that they are communicating/sharing information. The highlighted output from show ip eigrp focuses on some key information. First, you can again validate that the process ID is configured correctly (also referred to as autonomous system ID if a number
is used), and you can also see the status as running.

By default, EIGRP uses bandwidth and delay with K value modifiers to calculate this metric to choose the best route to install in the routing table (successor) for any given destination. We do not go deep into this calculation here, but it is important to note that K1 is the bandwidth modifier for calculation and K3 is the delay modifier for calculation, so by default in your output, you should see K1 and K3 set to 1 and all other K values set to 0.

Finally, you see the number of neighbors (peers) and interfaces participating. Though these numbers for peers and interfaces do not always match, as in the case of peering with multiple neighbors on a local-area network over one interface, it can help you understand the peering and interface configurations. In the final output from show ip eigrp neighbors 10.1.1.2, you can validate that the neighbors are up, how long they have been up, their IP address, and the interface in which the peering happened. Note one final thing about EIGRP (which you can see in the outputs) that differentiates it from other distance vector routing protocols: its hello and update methodology.

OSPF Configuration on NX-OS

The Open Shortest Path First (OSPF) Protocol is the final routing protocol to look at from a configuration perspective. In comparison to RIP and EIGRP, OSPF is considered a link-state routing protocol, and the following examples point out the differences in configuration, validation, and troubleshooting of this routing protocol from RIPv2 and EIGRP.

Example 21-11 shows the configuration of a single area (0) with routed interfaces, and
Example 21-12 explores configuring OSPF using SVIs for a single area (0).

	Created by Isaac Farias about 10 years ago

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