RE: [nsp] 2 ISPs, BGP and load-balancing

From: Ahmer Ghazi (
Date: Fri Dec 28 2001 - 02:54:34 EST

"maximum-path" would only install multiple routes in the routing table
if all the attributes are same and the routes are from the *same*
neighboring AS, so it won't serve the purpose of eBGP multipath
loadsharing in case of 2 different ISPs.
Ahmer Ghazi

-----Original Message-----
From: Rick Casarez []
Sent: Thursday, December 27, 2001 5:51 PM
Subject: Re: [nsp] 2 ISPs, BGP and load-balancing


    What kind of load balance are you looking for and which direction?
Inbound or outbound or both?

      If you want really load balancing you can, if your router can
handle it, run 'maximum-paths 2' global BGP command on your router. This
will allow your router to choose 2 best paths instead of the 1 (the
default). If you are receiving only partial routes from each provider
then you could run equal weight default routes pointing towards each and
what doesnt get captured from the provider announcements will be sort of
balanced out for you.
I would recommend the latter personally.

        For inbound load-balancing it is a little bit harder and would
involve tweaking attributes for subnets of your prefix (or multiple
prefixes) to the providers. That I would recommend doing until it works
like you want it to.


>From: TMS
>Subject: [nsp] 2 ISPs, BGP and load-balancing
>Date: Wed, 26 Dec 2001 06:52:08 -0500
>I have two 4mbps internet links connected to 2 diffrent ISPs. How
>I can create load-balancing between both ISPs ? At
>this moment my router configuration (Cisco 7206VXR, NPE-400)
>looks like that:
>router bgp 60000
> network
>neighbor weight 50
>neighbor remote-as 10000
>neighbor description ISP-1 (ex.UUNET)
>neighbor filter-list 1 out
>neighbor route-map SETMETRIC in
> neighbor weight 50
> neighbor remote-as 20000
> neighbor description ISP-2 (ex.AT&T)
> neighbor filter-list 1 out
> neighbor route-map SETMETRIC in
>ip as-path access-list permit ^60000$
>ip as-path access-list deny .*
>route-map SETMETRIC permit 10
>match ip address 1
>set metric 100
>access-list 10 permit any
>Any propositions ? Maybe I must set local-preference or
>as prepend for neighbors ?
>greets, TMS


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