From: Godswill Oletu (oletu@inbox.lv)
Date: Wed Jul 06 2005 - 15:33:52 GMT-3
John,
I think setting up iBGP between East and West should do this, without
setting up additional policies or tweaking. East will have an eBGP with
South and West will also have another eBGP with South.
If all links are up, the eBGP routes/paths will be preferred (lower AD) on
both East and West thus traffic will flow directly to South. If the link
between West and South fails, the iBGP routes will replace the eBGP routes
in West's routing table and traffics from West will flow through East to
South, the same will happen if the route between East and South fails.
However, you must have a separate link from East to West for this to happen
not dependent on the link through South.
----- Original Message -----
From: "John Darpino" <john.darpino@gmail.com>
To: "gstudy" <ccielab@groupstudy.com>
Sent: Wednesday, July 06, 2005 2:05 PM
Subject: BGP Route Selection in a single AS
>I have two geographically opposite locations in the same AS called
> East and West.
>
> Each of these two locations has a single link to the same location in
> a seperate AS. We'll call this location "South". These two links are
> in place for redundancy. Optimally I would like to set up policy that
> would point users local to East to egres to this South net over the
> East link and users local to the West to egres over the West. In the
> event of a failure of any one link, I'll need to have all traffic
> traverse the remaining connection.
>
> I have used LOCAL_PREF in the past to set policy on prefixes local to
> a given AS, but again, as this is a single AS, I do not know if I can
> impose a preference on one of two egres points within the same AS
> based on a given source.
>
> Thanks.
>
> --
> Entropy - it's a tough job, but somebody's got to undo it.
>
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