[c-nsp] ISIS Route Flapping Issue

[Peter Rathlev]

Hi David,

On Wed, 2008-11-05 at 11:08 -0500, David Jacobs wrote:
> I did a sh ip route X.X.X.X and at times it would say x.x.x.x/32 and
> other times I would just see x.x.x.x/16. Quite obviously this made
> life for my frame relay customers life misery.
> After trying all sorts of steps we could not get the flapping to stop.
> In a last ditch effort we offloaded our OC3 onto another router,( we
> are still using this router as a lifeboat.)

What did the box itself have in its routing table at this time? How does
the box lift the host prefix into IS-IS? Does a "debug isis rib
resdistribution" give any clues?

> To skip ahead, I ended up getting a new 7507 chassis, brand new RSP 4
> and brand new GEIP's and OC3 cards. I reconfigured the router with the
> same Ip and ISIS config and WHAMMO the same ISIS route flapping begins
> to happen. After many hours of troubleshooting one thing I did was
> change the ISIS NET address, once this was changed things went back to
> normal.

Brand new 7500 hardware? Where? ;-)

> Why would changing the NET address suddenly stop an ISIS route from
> flapping?

A shot in the dark, but you wouldn't happen to have another box with the
same NET on your network?

Regards,
Peter