BGP multi-path only works with *identical* prefixes, the only difference
between the paths permitted is the router-ID of the originating router.
Are you certsin that you are receiving identical routes from all the PoPs?
If you have four T-1s I would suggest that before worrying about
load-balancing, you seriously look at resilience in your uplink - ie split
your T-1s out over at least one other router.
As far as load balancing goes, and assuming that the PoPs are all pretty
equally connected, it is up to you how to weight the routes. A really
basic, semi-arbitrary way might be to match as-paths on each link as
transiting each of the top 4 Tier-1s:
UUNet - AS701
C&W - AS 3561
AboveNet - 6461
BBN - AS1
(not sure my details are entirely up to date, but open to comment)
and the set the local-preference to >100 for these paths on each router
this might be a starting point - it is a coarse grained way to split the
traffic, you can fine-tune from there. it may be worth checking those
AS-paths on each router to see whether any one of the four is best connected
to those routes.
hth
Andy
----- Original Message -----
From: "moe humm"
To:
Sent: Saturday, June 02, 2001 5:01 PM
Subject: BGP -Maximum Paths [7:6887]
> Hey gang,
>
> I have a question on maximum-paths in BGP;
>
> This is the scenario: 4 T1's running EBGP to our ISP in a multihome peer
> session; each of the circuits go to a different POP. Each of the peer
> sessions receive a partial routing table from our provider. What we have
> found is that load sharing (outbound to our ISP) is virtually
non-existant.
>
>
> well, i'm studying for BCSN and came across the maximum path feature, and
it
> seems like the solution.
>
> My question is this: we have enabled maximum-path 4 to load share between
> the four sessions. This, however has had a neglible effect. Does the
fact
> that we still hear routes from the provider from different pops affect
this?
>
> In other words, since the 4 pops are in a different geographical area, and
> therefore may send a different bgp table which in turns overrides the
> maximum path command.
>
> I want to try having the provider send a default route instead; the
thought
> being that our router will not have to decide on best paths, and leave
that
> to ISP router, but the powers to be don't want that (for some reason...)
>
> Does anyone have any suggestions?
> thanks all,
>
> moe
>
>
>
>
>
>
> _________________________________________________________________
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Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=6890&t=6887
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