Cisco BGP routing. Is it possible to force traffic out an interface depending on source address?
Posted on 2009-12-18
We have a Cisco Internet BGP router which peers with two different ISP's. Under normal operation we are load balancing traffic between the two carriers using route maps and odd/even AS paths. Everything works well.. However, We now need to route a particular local network out of a particular carrier interface.
BGP Router interfaces FYI-
GIG1/0 - Various Public networks (This is our inside int connected to L3 switches)
Fastethernet 2/0 - 40Mbps BT Peering
Fastethernet 2/1 - 100Mbps Telewest Peering
For example, We need network A.B.C.D/24 to route via Telewest at all times (Fa2/1) unless there is a failure. But all other networks should loadshare as normal... I thought of maybe using PBR but I think we'll lose the failover to BT if we have a problem?. Incoming traffic is ok as I am using AS Pre-Pending for the A.B.C.D/24 network via Fa2/0. So Fa2/1 naturally becomes the best route for incoming traffic..
It's how to achieve the outgoing traffic which is stumping me?.. I know I can use local-preference/MED but that will apply to all traffic not just the traffic originating from the A.B.C.D/24 network..
Any ideas guys?
Thanks in advance for your help.