A few days ago I've been involved in an interesting EIGRP-within-MPLS/VPN troubleshooting session. I wanted to reproduce the behavior in the lab, so I set up a simple EIGRP lab … and realized that it's been a while since we wrote the MPLS and VPN Architectures, Volume II, which covers EIGRP used as PE-CE routing protocol. To make things more interesting, a few details have changed in the meantime; you have to configure the following features to get EIGRP running within MPLS/VPN environment:
- The autonomous-system command within the VRF address family is mandatory, even if the VRF AS number matches the EIGRP process number.
- The default BGP-to-EIGRP redistribution metric has to be configured, otherwise remote EIGRP routes will not be redistributed even though they have EIGRP metric encoded in extended BGP communities.
- Things work best if you disable auto-summary on PE-routers.