I wanted to do some analysis of the EIGRP topology table last night, so I fired up a small lab. I was especially interested in how external routes appear there and compare to internal entries. Like all good scientific endeavors, the whole thing got derailed when I made a realization.

Here’s the lab I set up. You can ignore the IPv6 info for this exercise.

It’s a simple little thing.  All the networks you see are included in EIGRP 100 for simplicity.  I limited the network statements to 192.0.2.0/24 to keep my options open. I went ahead and added Loopback100 on R3 with an address of 3.3.3.3/32 and added a redistribute connected with a route-map to get the route out in the wild.  Here’s what I had.

Feel free to correct.

Study Questions

• The obvious first question involves the common LSA types and their function.  Can you list them?

Type-1 - Router - Lists each router their connected IP addresses Type-2 - Network - Lists all the transit, or multiaccess, networks Type-3 - Net Summary - Defines a  host route for interarea routes; this is from the ABR Type-4 - ASBR Summary - Defines a host route for an external (to OSPF) route; this is from an ASBR Type-5 - AS External - Lists the networks advertised into OSPF from external sources (redistribution) Type-7 - NSSA External - External routes injected into a not-so-stubby area