[nsp] BGP issues after upgrading IOS versions

Danny McPherson danny at tcb.net
Mon Aug 25 21:29:12 EDT 2003

On Monday, August 25, 2003, at 03:58 PM, Scott Lambert wrote:

> router bgp 4276
>  no synchronization
>  bgp log-neighbor-changes
>  network mask

> -ip route Null0 240
>  ip route Null0 255

When a "network" statement is configured the BGP process checks
to ensure that a local IP RIB (& FIB) entry exists for the
concerned *prefix* before generating an update and considering
the route as feasible.

In the "working" configuration there was a "hold-down" (or "hold-up",
depending on who you're talking to :-) route for with
an administrative distance of 240, which is fine.  It looks as if
there was also a route for the same prefix with an administrative
distance of 255 (which means the router doesn't trust the source and
won't use the route to populate the RIB).

In the "non-working" configuration the route with the administrative
distance of 240 is gone and only the "useless" route (i.e., the route
with the administrative distance of 255) remains.  As such, when BGP
checks for a RIB match before generating the /19 advertisement it

I don't see any obvious indicators in the bug lists for these IOS
versions that would suggest why the 240 route would be removed, but
nonetheless, I'd suspect that was at least part of your problem.



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