[c-nsp] BGP Multi-homing

[Tim Vollebregt]

Hi Bob,

There are a lot of configuration options to do this.

A simple solution for this, hereby I assume that your secondary neighbor is accepting (default) bgp communities.

Primary neighbor (default route): 1.1.1.1 AS10
Secondary neighbor (full table): 2.2.2.2 AS20
Local AS: AS30
Local prefixes: 3.3.3.0/24 and 4.4.4.0/24

Create as-path acl:
ip as-path access-list 2 permit _20$

Create no-export access-list (specify your local/customer prefixes here):

ip prefix-list no-export seq 1 permit 3.3.3.0/24
ip prefix-list no-export seq 2 permit 4.4.4.0/24
ip prefix-list no-export seq 10 deny 0.0.0.0/0 le 32

Create route-maps:
--inbound--
route-map secondary-in permit 5
match as-path 2
set localpref 105
route-map secondary-in permit 10
set localpref 80

--outbound--
route-map secondary-out permit 5
match ip address prefix-list no-export
set community no-export additive
You don't have to change anything in the configuration of your primary neighbor, only put the in and outbound route-maps on the bgp session:

Router bgp 30
Address-family ipv4
Neighbor 2.2.2.2 send-community
Neighbor 2.2.2.2 route-map secondary-in in
Neighbor 2.2.2.2 route-map secondary-out out

Please make sure you also have an normal outbound prefix list on the session.

If your secondary neighbor has a lot of 'local' routes which you want to send traffic to, but these routes are not originated from AS20. You should ask them if they can specify a customer bgp community. Afterwards you can match that community in the inbound route-map and set a localpref of 100+ to it.

Regards,

Tim


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of bobby hajhassan
Sent: dinsdag, 13 april, 2010 10:01
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] BGP Multi-homing


Turning up a backup BGP session with a secondary provider. Currently accepting a default route from my primary provider and will have full table from secondary. Would like to continue to have the primary provider as the preferred inbound/outbound path once i've turned up the secondary session. I would however like to prefer the local only routes from my secondary provider and have all other routes preferred through my primary. Config templete would be great...any help is appreciated.
 
Thanks
Bob




 
 		 	   		  
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