When troubleshooting an EIGRP network, one of the first things to verify is that all routers that are participating in the EIGRP network are configured with the same autonomous system number. The router eigrp as-number command starts the EIGRP process and is followed by a number that is the autonomous system number. The value of the as-number argument must be the same in all routers that are in the EIGRP routing domain.

Figure 1 shows that all routers should be participating in autonomous system number 1. In Figure 2, the show ip protocols command verifies that R1, R2, and R3 all use the same autonomous system number.

EIGRP for IPv6

Similar commands and troubleshooting criteria also apply to EIGRP for IPv6.

The following are the equivalent commands used with EIGRP for IPv6:

Note: At the top of the output, “IP Routing is NSF aware” refers to Nonstop Forwarding (NSF). This capability allows the EIGRP peers of a failing router to retain the routing information that it has advertised, and to continue using this information until the failed router resumes normal operation and is able to exchange routing information. For more information refer to: http://www.cisco.com/en/US/docs/ios-xml/ios/iproute_eigrp/configuration/15-mt/eigrp-nsf-awa.html