North American Network Operators Group
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Re: Global Crossing Contact / BGP and SONET interaction question

  • From: Niels Bakker
  • Date: Wed Jul 26 05:22:42 2006

* [email protected] (Randy Epstein) [Wed 26 Jul 2006, 07:44 CEST]:
Recently my BGP session has started flapping on the GX circuit... It looks something like this:

Jul 21 21:33:32.703 UTC: %BGP-5-ADJCHANGE: neighbor 67.17.168.73 Up

There are no other log entries during the periods when this occur. Unfortunately this causes enough prefix flaps that any prefixes which are preferred through GX are damped for like a half hour by certain providers as my BGP routes get added/withdrawn through the GX link.
I don't have an answer to the root cause of your problem, and I'm not looking for a discussion on route dampening (there are enough debates on this issue to make your head spin), but may I suggest you raise your hold timers to prevent your BGP sessions from going down on short disturbances as these?

Wrong error condition - hold timer isn't triggered when the interface for a directly connected neighbor goes down.

You'll want Global Crossing to configure a hold-timer on their Juniper or a carrier-delay on their Cisco router. Or configure "no bgp fast-external-fallover" but that has more side effects.


-- Niels.