notes: Troubleshooting EIGRP Route Summarization

Summarization is extremely important in a well-designed EIGRP network. Summarization is one of the few weapons to prevent stuck in active problems. Most summarization problems are the result of a misconfiguration of the router.

1.  EIGRP Summarization Route Problem—Cause: Subnetworks of Summary Route Don't Exist in Routing Table.


verification:

show run
show ip route

Solution:

The solution to this problem is to configure an interface that falls in the summary range. You can configure a loopback interface with address w/in the summary range to generate the summary route configured.


2.  EIGRP Summarization Route Problem—Cause: Too Much Summarization
Another EIGRP summarization route problem stems from when the summary route covers more subnetworks than exist.


debugs and verification:

show ip route x.x.x.x

solution

This problem is more of a design issue. The main issue is that Router B's summary route is too broad and includes nonexistent subnets. Also, Router A is sending a more general summary route (default route) to Router B. The solution is to have Router B send out only the summary route that covers the 172.16.1.0 through 172.16.15.0 networks.