[nsp] elusive OSPF problem

From: Brian Wallingford (brian@meganet.net)
Date: Sun Sep 20 1998 - 00:15:03 EDT


Not sure if I'll be able to explain this well, but:

We've got a "triangular" network - three geographically separate
borders. Other facts are as follows:
        We're running IBGP between all, and OSPF internally.
        We're using loopback interfaces for IBGP updates.
        Each border knows, via ospf, how to find it's neighbors' loopbacks -
verified via sh ip ro <neighbor's lo0> and sh ip ospf neig <neigbor's
lo0> - everything seems normal.

The problem: All three routers *seem* to be fine ospf-wise. Router A
is speaking IBGP with router B and router C. Router B is speaking IBGP
with router A and router C. Router C is speaking IBGP with router B,
but not router A. Further analysis shows a failure to establish a TCP
session with router A. Using the serial interface address instead of
the loopback for BGP updates restores TCP/IBGP. (Again, according to
OSPF, the route to the loopback _is known_)

I'm stumped. Hopefully I'm overlooking something obvious - any ideas
would be appreciated :)

Thanks,
Brian

-- 

Brian Wallingford Network Operations Manager Meganet Communications, TCIx, Inc.



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