BGP Configuration

Unanswered Question
Mar 28th, 2008

Hi All

I have three sites (A,B,C) connected through MPLS-VPN using protocol BGP with AD 20(EBGP).Site A is our central site and we have secondary link (VSAT),Site A to B and A to C. Now I want to use same protocol for secondary link and traffic should be move through MPLS-VPN while both the link up.

for mpls link config like blow

router bgp 63590

network x.x.x.x mask x.x.x.x

network x.x.x.x mask x.x.x.x

neighbour x.x.x.x remote-as 9829

all the sites (A,B,C) having bgp AS 63590

How to configure secondary link (VSAT) using same protocol ?

I have this problem too.
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Edison Ortiz Fri, 03/28/2008 - 12:00

The VSAT peering would be considered an iBGP as there isn't a provider router in the middle of the connection as the MPLS-VPN.

While eBGP is preferred over iBGP when all attributes are being equal, on this case, the AS_PATH will be shorter on iBGP so those routes will be preferred.

You can configure a route-map on each router and use AS Prepending on routes being advertised for the VSAT neighbor.

router bgp 63590

neighbor [vsat_peer_router] remote-as 63590

neighbor [vsat_peer_router] route-map AS-PATH-OUT out

route-map AS-PATH-OUT

set as-path prepend 63590 63590

HTH,

__

Edison.

tyagi.vineet Fri, 03/28/2008 - 22:51

Thanks Edison

I have configured the same but still most of the route are learned by AD200 (iBGP). please help me out.

royalblues Sat, 03/29/2008 - 01:03

Try using the local preference / weight attribute to prefer the MPLS routes

router bgp 63590

neighbor < 9829

neighbor route-map local-pref in

route-map local-pref permit 10

set local-preference 120

You need to configure it at both ends

HTH

Narayan

tyagi.vineet Sun, 03/30/2008 - 23:42

Thanka Narayan

but i think this will work when both the routes comming from iBGP.

weight attribute also i have configured but no change. I am thinking whatever attribute i am configuring is not allowed by sevice provider of MPLS-VPN.

am i right or not ?

royalblues Sun, 03/30/2008 - 23:50

It should work... can you post your configurations

The Local Preference and Weight attribute is local to your router to make a decision on the routing. It has nothing to do on the Providers MPLS VPN

HTH

Narayan

Edison Ortiz Sat, 03/29/2008 - 06:17

Did you configure the AS Prepend on all VSAT neighbors? Doing it on just one end won't work.

Can you post the portion of the config from the 3 routers ?

Edison Ortiz Sat, 03/29/2008 - 11:47

Ok, forget AS_PATH prepending. It won't work on this situation as they are iBGP neighbors. Please follow Narayan's advise and use local-preference instead.

Sorry for providing the wrong information before.

Regards,

__

Edison.

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