BGP - Peer AS to multiple ISP 's and Load Balancing - Cisco

Posted on 2011-04-30
Last Modified: 2012-05-11
Scenario: customer has its own BGP AS (say AS 1234)and is peering with two separate ISP, with two seperate routers.  They discover that one of the links is being utlized 70% and the other one 30%.  What options do they have to balance out inbound utilization?  I have found a few articles from Cisco that states a Route Map can be created to artifically prepend the AS-Path attribute for several of the IP prefixes that are be advertised with 1234 1234 1234 and this should shift a portion of the traffic to the other ISP by making the AS-Path hop count less than ideal.  What other methods could be used?
Question by:agent2592
    1 Comment
    LVL 24

    Accepted Solution

    your options are a bit limited for inbound traffic; typically you can not control incoming traffic, but you can however, influence incoming to your AS by sending MED, communities, and pre-pending as you have already mentioned. Pre-pending is by far the easiet. This of course is very limited on the prefixes you are sending out. You are not able to influence traffic by source prefixes or ASes or any other mechinism (You have no control over source inbound routing), you can only tell your upstream on where to send traffic to your prefixes and based on their routing policy they may or may not honor your influenced information.

    Here is some reading if you have not already found it:


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