[nsp] BGP issues after upgrading IOS versions

[Danny McPherson]

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

> router bgp 4276
>  no synchronization
>  bgp log-neighbor-changes
>  network 216.223.192.0 mask 255.255.224.0

> -ip route 216.223.192.0 255.255.224.0 Null0 240
>  ip route 216.223.192.0 255.255.224.0 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 216.223.192.0/19 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
fails.

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.

HTH,

-danny