BGP Issue

Unanswered Question
Jan 29th, 2008

I have got two Links through BGP n internal i am using ospf, one i am using as primary n other as backup.If the primary goes down all the traffic is going VIA backup n when it Primary link comes back, the traffic is still not getting shifted.

I have to shutdown that primary interface or else its taking 2000-3000 ms delay, what might be the issue ???

I have this problem too.
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sibgathullah Tue, 01/29/2008 - 00:52

when the primary links work, i get the delay of 15-35ms, but after this problem i am getting 2000-3000ms.So here is the main issue Narayan.

guruprasadr Tue, 01/29/2008 - 02:58

HI,

#sh ip bgp

Output shows:

A ">" indicates the path currently being used and if the link fails the other link is used.

Failover can be slow in BGP. Keepalive is 60 secs & Hold time is 180 secs. Potentially 180 secs could pass before BGP detects a failed BGP Connection and switches to other Link.

Eitherway, you can improve the failover time by resetting the BGP Keepalive and hold time with the "timers bgp" command.

For eg: timers bgp 3 9 sets the keepalive to 3secs and hold time to 9 secs.

PLS RATE if HELPS

Best Regards,

Guru Prasad R

vgrigaliunas Fri, 02/01/2008 - 09:49

You may want to try BGP Bidirectional Forwarding Detection (BFD), which allows failure detection in the millisecond range.

Rick Morris Fri, 02/01/2008 - 09:39

When links failover in BGP it is not an instant thing. As stated there are timers. The main question is does your traffic stop when the primary link comes back up or is it just the delay the only issue? If your traffic stops then you have another issue that needs to be addressed and the convergence issue is not really an issue rather a symptom.

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