Global Crossing Contact / BGP and SONET interaction question

Niels Bakker niels=nanog at
Wed Jul 26 09:21:20 UTC 2006

* repstein at (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 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providers as my BGP routes get added/withdrawn through the GX link.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.

More information about the NANOG mailing list