I had a bizarre event occur on Thursday night/Friday morning, and this is likely the culprit. I peer with AS701. At approximately 11:15PM PDT or thereabouts (2:15AM EDT), the 7507 which provides my connectivity to uu.net went belly-up in a very strange way. The BGP session with 701 showed active, with full tables; existing TCP connections stayed up. However, it appeared that all new connections inbound from 701 were being dropped on the floor, and my outbound traffic with them dropped from 40mb/sec down to about 5kb/sec. The same router was also handling a secondary connection to pbi.net; because the BGP stayed active and in a supposedly functional state, traffic didn't get routed in that direction as it should've been. I had to reload the router to get it to function properly. Very odd. Nothing in the logs, etc. The router just essentially went on strike, and I've no idea why. I don't run IS-IS, needless to say, especially with a foreign AS. This particular 7507 was running an 11.3.x CC-train IOS, and hadn't had any of the ISO/CLNS family of protocols enabled, ever. This is a bit earlier than the timeframe Sean cited, but I don't think it was a coincidence, either. ----------------------------------------------------------- Roland Dobbins <rdobbins@netmore.net> // 818.535.5024 voice -----Original Message----- From: Neil J. McRae [mailto:neil@COLT.NET] Sent: Monday, October 30, 2000 1:28 AM To: sean@donelan.com Cc: smd@clock.org; nanog@merit.edu Subject: Re: IS-IS protocol implementation problem

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. Regards, Neil.