From: Stephen C. Feldberg (scfeldberg@xxxxxxxxxxx)
Date: Wed Dec 26 2001 - 11:52:15 GMT-3
Any route reflection configured in the transit AS? Rember that OSPF and BGP
have issues when sync is left enabled and the OSPF route needs to be
propagated between route reflector clients. The "fix" is to move the
redistribution point, or implement another IGP.
Steve
----- Original Message -----
From: "EA Louie" <elouie@yahoo.com>
To: <ccielab@groupstudy.com>
Sent: Tuesday, December 25, 2001 3:54 PM
Subject: BGP and IGP redistribution - ccbootcamp8
> Findings from ccbootcamp 8 that I wanted to share with you and get some
> opinions about.
>
> The scenario has 3 BGP AS'es with one acting as a transit AS. The rules
> called for synchronization on 3 of the BGP routers.
>
> I found that redistributing OSPF into BGP on a router that is not
synchronized
> did not allow the BGP routes to be sync'ed at a downstream iBGP neighbor,
> which prevented those routes from being propagated to the next eBGP
neighbor.
> The exact error message was found in deb ip bgp updates, which said "No
valid
> path for a.b.c.d", and also from 'show ip bgp a.b.c.d' which would
indicate
> the route was not sync'ed. Can anyone explain to me why, when the bgp
routes
> are in the ip routing table, I'd get these messages, which essentially
prevent
> an iBGP to advertise routes to a eBGP neighbor? It looks like it has
> something to do with bgp next-hop addresses being the same in the IP RT
and
> the BGP table, but I can't be sure, and wouldn't know how to make them the
> same even if I were sure.
>
> Now, if there's another way to solve this problem, I'd love to hear about
it,
> but all I did to solve it was move the OSPF --> BGP redistribution point
to R6
> (for those familiar with this lab). I had originally done this at R1 (a
route
> reflector), where 'no sync' was allowed.
>
> I also found that redistributing the eBGP routes into OSPF (or other IGP)
at
> the iBGP entry points is a good practice, and only requires a small
> access-list and route-map to accomplish.
>
> -e-
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