North American Network Operators Group

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Re: IS-IS protocol implementation problem

  • From: Neil J. McRae
  • Date: Mon Oct 30 04:30:57 2000

> At approximately 7:37am EDT on Friday, about 258 Cisco 12000's on UUNET's
> primary backbone reloaded. This appeared to be isolated to routers
> in ASN 701. It disrupted reachability to about 15% of the world-wide Internet
> based on data from Matrix measurements.  A contributing cause was a bad
> IS-IS packet which confused certain IOS versions in the 12.0 IOS software
> train. I haven't heard what the root cause was or what originated the
> bad IS-IS packet. The Cisco bug id is CSCdr05779. Any provider running the
> affected IOS version may be vulnerable depending on what the root cause
> turns out to be.
> Although the bad IS-IS packet didn't propagate to other providers, several
> other providers did report BGP resets and route flaps about the same time.

If a large AS such as AS701 starts flapping I wouldn't be surprised
if other ASes start seeing BGP resets and route-flaps. Could be
that crud routing information was exchange when that chaos started
[jeez 258 routers I'd hate to have been the on duty NOC guy on that
morning :-)]

Interestingly though we still see alot routes with bad AS-PATH information
people should be setting more stringent configurations on the routes
the learn and subsequentally pass on to avoid this.