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routing problem (with GRE tunnel)

My cisco router are connected to 5 sites with Frame-relay and i also setup a GRE tunnel (tunnel 1)over the internet for one of the sites for backup.

Routing protocol EIGRP.

Everything is working great but when i do a show ip eigrp topology for any of the sites it always show me two routing path 1) the original Frame-relay link and 2) tunnel 1 with hop 3

any idea why ?


Re: routing problem (with GRE tunnel)

Both paths are valid, loop-free alternates to reach that destination. This is what you want (to have the backup path a feasible successor to the primary path). You may need to adjust the bandwidth and delay on either the tunnel or the primary link to ensure that the correct path is considered primary (if that is not already the case, see what "show ip route" gives as the next hop).

As to "why" . . . you may want to curl up with a book explaining how EIGRP does routing and, in particular, the concept of feasible successors. Hint, those who don't learn what a feasible successor is tend to have a hard time getting EIGRP to work optimally in non-trivial topologies. For a start, check out the EIGRP white paper on Cisco's web site. An excellent (and not too long) explanation of everything you need to know about EIGRP. Or you can read the blurb on EIGRP routing in the routing protocols chapter of my book, but that assumes more familiarity with routing protocol principles than the Cisco white paper.

Good luck and have fun!

Vincent C Jones

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