Drew Weaver wrote: > Howdy all, > > Last night I had an interesting encounter on one of my 6509s /w SUP7203-BXL. > > This switch has 3x iBGP sessions with full internet tables and is also > running OSPF. > > Two of the three iBGP sessions randomly dropped with: > > %BGP-3-NOTIFICATION: sent to neighbor x.x.x.3 4/0 (hold time expired) 0 > bytes, I also noticed that during this period OSPF dropped with Neighbor > Down: Dead timer expired > > > and then re-established, and then failed again, and re-established, and > failed again, and so-on, and so-on. > > I checked the physical interfaces between this 6500 and the two GSR 12000s it > peers with and there were no errors, there was also no obvious spike in > traffic that would account for latency that might cause the hold timers to > expire. I remember when this system first came online it took a really long > time for it to download the full internet tables from the upstream GSRs and > also during that time there was a lot of CPU time being eaten up, I am > wondering if maybe the first session failing caused sort of a 'performance' > domino effect which then caused everything else to fail, the issue eventually > corrected itself and stabilized. > > This particular box is running 12.2(18)SXF17 so I am less likely to believe > it is a software bug. > > Does anyone have any tips on both how I can avoid the hold timer issue > altogether
I dont think your issue is bgp and it's hold time - if ospf session drops then so will BGP session. Are you sure your upstream GSR's did not fail-over? If so NSF might help you http://www.cisco.com/en/US/partner/docs/ios/iproute/configuration/guide/irp_bgp_adv_features_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1056241 If you have unstable IGP, try to figure out why, if you cant, dampen. If that doesnt help, disable next-hop address tracking http://www.cisco.com/en/US/partner/docs/ios/iproute/configuration/guide/irp_bgp_adv_features_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1056441 Regards Dave > and also how I can make it so that if a session does go down and re-establish > it doesn't totally nail the CPU while it's trying to re-establish/download > the routes? A long time ago I also read that increasing the MTU on both ends > of a circuit can make BGP tables download faster, I don't know if that's true > or not, has anyone else found that? > > thanks, > -Drew > > > _______________________________________________ > cisco-nsp mailing list cisco-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
