BGP to influence outbound traffic

[hlee]

Hi,

If i have a single BGP router connected to 2 different ISPs, i can use 'local Pref' to influence the outbound traffic route.

But what should i do if i have 2 routers, each connecting to 1 ISP peer each? And both of my routers are linked together internally within my network.

Thanks

[atif.awan]

You would still use local preference. In the first case when you had a single router you could have used either local preference or the Cisco specific Weight attribute. But when you move to multiple routers you use local preference to affect outbound traffic. Your two routers will have an IBGP session between them and will pass on their local preference settings to each other; this will control the exit point for a specific route.

[vladrac-ccna]

Check the following link might help you:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml#localpref

Hope it does,

please remember to rate helpful posts.

vlad

[sean]

If you have two separate ISPs, I wouldn't influence the outbound path. I would let BGP choose the best path. If your bandwidth is not balanced on each connection or you are wanting to use a primary and secondary setup, then local pref would still work for you. Hope this helps.

[jeffbriones]

Hi guys,

What if my setup would be two bgp links connected to a single ISP using a single router. What attributes can i used to influence outbound traffic?

---------

Router BGP ISP

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tnx

jeff

[atif.awan]

You should not introduce the complexity of BGP in this scenario. Configuring two default routes will serve you well.

[vladrac-ccna]

In this case you can use weight (cisco propietary) to change the metrics inside this single router.

"The weight attribute is a Cisco-defined attribute. This attribute uses weight to select a best path. The weight is assigned locally to the router. The value only makes sense to the specific router. The value is not propagated or carried through any of the route updates. A weight can be a number from 0 to 65,535. Paths that the router originates have a weight of 32,768 by default, and other paths have a weight of 0.

Routes with a higher weight value have preference when multiple routes to the same destination exist.

"

HTH,

if it does, please rate this post.

vlad

[sean]

You could also work with your ISP to have them change the MEDs on each of the links to influence the return path for your traffic. Hope this helps.