[91417] in North American Network Operators' Group
Re: Global Crossing Contact / BGP and SONET interaction question
daemon@ATHENA.MIT.EDU (Niels Bakker)
Wed Jul 26 05:21:50 2006
Date: Wed, 26 Jul 2006 11:21:20 +0200
From: Niels Bakker <niels=nanog@bakker.net>
To: nanog@merit.edu
Mail-Followup-To: nanog@merit.edu
In-Reply-To: <000601c6b076$6d6b0ec0$6401a8c0@D3M1BS91>
Errors-To: owner-nanog@merit.edu
* repstein@chello.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 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providers as my BGP routes get added/withdrawn through the GX link.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.
