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BGP two paths question

velimirmkd
Level 1
Level 1

Hi,

Let's say I have my system connected to two bgp peers. The best path is always through one of the peers. Having in mind that BGP can only load share and not load balance will the link to the second bgp peer (that normally has no traffic) pick up some of the traffic in case the first link ( that holds the best path) gets filled up (clogged) ?

Thks

5 Replies 5

No,

Already been there. There is no answer to the question :-))

...

saluko
Level 1
Level 1

The idea of load share is that you specify which traffic (using route map) goes via a particular link. If you do not specifiy this then the second link will not load share.

osam
Level 1
Level 1

The answer to your question is simply NO, unless it is really clogged to an extent you no more can ping the remote end (the best path peer). As long as you are receiving BGP updates from your peers, there is no way this can happen.

That was the simple answer. However, in some cases (depends on the configuration) your traffic may switch to the secondary peer. If your first peer (best path) link is continuously utilized to an extend that the remote end see it up and down, it may consider the link flapping, and if this peer (best path) has dampening enabled, then it will dampen your route for a period of time causing your router to switch the traffic to the secondary path.

We can go on and on for similar scenarios. I would suggest you manually distribute the load among both link by prepending some of your networks or changing the weight or something. Please check my reply to a similar question asked earlier in this forum,

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&type=bookmarks&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.ee81164