[c-nsp] BGP Upstream in different interfaces.

[Alexandra Alvarado]

Hello,

To have Internet access with my 3 providers I do the next:

First Provider: I establish a BGP session with the AS provider
Second Provider: I use IBGP with ours intermediate router (to reach the ISP)
this router is between my multihome router and the provider router.
Third Provider: I use IBGP witch ours intermediate router (to reach the ISP)
this router is between my multhome router and the provider router.

The Intermediate router to the second and third provider is not the same
router.

I receive the default gateway in my multihome router.


Because I have 2 IBGP sessions and 1 BGP session, apply the bellow example?
And if not, what is the configuration to balance the upstream traffic?


Thanks


Alexandra Alvarado


-----Mensaje original-----
De: Michael Smith [mailto:mksmith at noanet.net] 
Enviado el: Domingo, 13 de Febrero de 2005 05:43 p.m.
Para: Alexandra Alvarado; cisco-nsp at puck.nether.net
Asunto: Re: [c-nsp] BGP Upstream in different interfaces.

Hello:


> From: Alexandra Alvarado <aaaa at telconet.net>
> Date: Mon, 14 Feb 2005 02:11:41 -0500
> To: <cisco-nsp at puck.nether.net>, 'Alexandra Alvarado' <aaaa at telconet.net>
> Subject: [c-nsp] BGP Upstream in different interfaces.
> 
> Hello,
> 
>  
> 
> I have three ISP Provider for backup, and via BGP I have been configured
> three network group each one preferred for each provider and as backup for
> the others (adding as-path prepend), it works well for download  but for
> upstream all the traffic only goes for one preferred interface (local
> preference 120).
> 
>  
> 
> I would like to know if is possible to choose the upstream traffic by
> selected networks without applying "service policy" in the interface but
by
> BGP in the neighbors?
> 
>  
> 

Sure.  Let's say you wanted to prefer AS701 out to Peer A and AS1239 out to
Peer B, everything else is equally balanced.

ip as-path access-list 2 permit .*
ip as-path access-list 5 permit _701_
ip as-path access-list 6 permit _1239_

route-map PEER-A-IN permit 5
match as-path 5
set local-preference 120

route-map PEER-A-IN permit 10
match as-path 2
set local-preference 100

route-map PEER-B-IN permit 5
match as-path 6
set local-preference 120

route-map PEER-B-IN permit 10
match as-path 2
set local-preference 100

router bgp xxx
neighbor peer.a.ip route-map PEER-A-IN in
neighbor peer.b.ip route-map PEER-B-IN in

The regexp in the access list above could certainly be refined.  You could
also add other AS to the existing as-path access-list above, or add a new
access-list and make it a different local-preference within the route-map.

Mike
-- 
Michael K. Smith               NoaNet
206.219.7116 (work)         866.662.6380 (NOC)
mksmith at noanet.net      http://www.noanet.net