route BGP monitoring

Unanswered Question
Aug 8th, 2007


I am new for BGP. One internet route link will be down with AT&T notice, traffic should go with other route and ISP. How to monitoring BGP traffic and see it is work to other isp? When Att line back to normal, how to make traffic back to ATT? please help.



I have this problem too.
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Pavel Bykov Thu, 08/09/2007 - 00:32

It depends on your setup. There are many ways to do it.

1. You can adjust timers on (delay) on all interfaces of one router to make it less preferable to interior gateway protocols. (for outbound traffic)

2. You can prepend your own as number to as-path attribute of all your routes to make it less preferable (for inbound traffic - using route-map)

3. You can set local preference attribute of incoming routes to prefer certain ISP (for outbound traffic)

There are a lot of scenarios.

Please refer to following BGP MultiHoming scenarios:

Here is a collection:

Hope this helps.

Please rate all helpful posts.

benma2423 Thu, 08/09/2007 - 10:17


We have two cisco routes do a bgp and HSRP, one link is with ATT, other link is with Internap. With Att maintain, line with AT&T will be down tonight, by setup, when link down with ATT, traffic should go with Internap.

I just run show ip bgp summary and show ip bgp route-map and see bgp is up and working.

I worry when ATT line down, traffic go with Internap, then when ATT line back, does traffic automatic back to ATT line, or still keep on the Internap, I have to enter command to make traffic back?

I hope I can get some single command to mornitoring bgp traffic see traffic where is going.



Route_reflector Thu, 08/09/2007 - 20:20


you can use trace command to find these..

trace to check the upload path.. OR

You can use "Show ip route" & " show ip bgp "to find out from where you learning the default route to send upload traffic.

You can also do a trace from to ur IP and see how u incoming traffic selects the path..

You can also use looking glasses and verify through the as path, if you have your own AS.


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