Troubleshooting the exchange of IGRP or RIP route information is a reasonably simple procedure. Routing updates are either propagated or they are not, and they either contain accurate information or they do not. The added complexity of EIGRP means an added complexity to the troubleshooting procedure. Neighbor tables and adjacencies must be verified, the query/response procedure of DUAL must be followed, and the influences of VLSM on automatic summarization must be considered.
This section's case study describes a sequence of events that typically can be used when pursuing an EIGRP problem. Following the case study is a discussion of an occasional cause of instabilities in larger EIGRP internets.