Internet Core Protocols: The Definitive Guide

Router Discovery

If you are seeing a lot of ICMP Redirect error messages in conjunction with Router Discovery, then you are not experiencing a problem (this is almost by definition). It is the prescribed behavior for the Router Discovery Protocol.

Remember that network devices will only choose a single default router, based on the preference values that are advertised by routers when they respond to Router Solicitation query messages. In this model, hosts will use that router for all non-local datagrams until they are informed of a better router for a specific destination system. Therefore, if your network has multiple routers, you will see a multitude of ICMP Redirect error messages on your network, as the devices learn about the various routers and the paths they support.

It may be that you have given the wrong router the highest preference value, and that by assigning a higher preference to another (more frequently used) router, the number of ICMP Redirect error messages on your network could be reduced. Another option would be to concentrate your routers together, allowing only one router to serve the local segment. This would essentially cause all traffic to go through the one remaining router, which would eliminate all ICMP Redirect traffic on the local segment.

For more information on Router Discovery, refer back to Section 5.1.4.4.