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New Member

BGP configuration for New AS with 3 Internet Links!


I am going to configure a new AS number in a big organization. The

organization will be using 3 links form three different ISPs.

Only one (ISP-1 ) will be advertising the organization routing


The ultimate goal is to do load balancing ((50 % - 30 % - 20 %) over the 3

links in both ways (in coming and out going) . Can this be achieved and


If this cannot be done what is the best ways to utilize the three links

for such organization.

Thanks a lot


  • Other Network Infrastructure Subjects

Re: BGP configuration for New AS with 3 Internet Links!

BGP has a rich set of attibutes using which you can achieve load-balancing. Load balancing for outgoing traffic will depend on how you learn your routes from the service providers and how you advertise those routes within your AS either using IBGP or an IGP. You can implement a good load balancing scheme if you are learning full internet routes from your providers or atleast partial routes and then use Local preference attribute to influence routing decisions by running IBGP within your AS. You can use the MED attribute to influence incoming traffic coming to your AS from outside. But, since you are saying that only one of the ISPs will be advertising your organization's routes, you may not be able to achieve the desired load balancing for the incoming traffic. Sam Halabi's book 'Internet Routing Architecture's has lot of good examples on Load balancing using BGP. The following link has has few examples for load balancing :

New Member

Re: BGP configuration for New AS with 3 Internet Links!

salamo 3alekom

i think u will need the 3 ISP to advertise ur networks, coz how will you load balance between them while they don't know ur route..

and beside using the MED attribute to controle the incoming traffic , i faced a case like this and i used route map with AS prepending to achieve the percentages u need in load balancing ur traffic plus having it backuped ..

but u will need to divide the networks in accordance to the percentages u need..i mean something like if u have 10 class C networks...u advertise 5 to ISP-1, 3 to ISP-2 and 2 to ISP-3..with a route map for prepending these routes to provide load balancing and backup at same time..

hope this helps


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