Multiple ISP connection and IP advertisement

Unanswered Question
Aug 3rd, 2010
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Hi All,

Have a little challenge using multiple isp internet conection.  I had ISP A which was advertising my ip block (with my ASN), i've however added ISP B, and have peered with their network (BGp) and thus they are also advertising my IP..  however, i realised that all request to my ip block from the internet goes through ISP A. but i want ISP B to be my Primary ISP  since am getting more bandwidth from them. how do i check my ip advertisement with ISP B and what do i need to do so that inbound traffic primarily traverse ISP B....

Thanx for help

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Chetan Kumar Ress Tue, 08/03/2010 - 11:52
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Hi Daniel,

Using Multiple ISP is reference to BGP  Multihoming ,

To manipulate to advetisement in BGP you should user BGP attributes . Below are the detail .

From Inside to Outside use : Local Prep

From Outside to Inside use  : Prepend AS

In your senario if you want to user ISP B as a primiary link then you should configure AS prepend with ISP A . So over internet the route will prefered from ISP B becasue of shortest AS Path.

Please refer for sample lab for same :


Chetan Kumar


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