[c-nsp] Sending traffic over different paths

[Oliver Boehmer (oboehmer)]

Kristofer Sigurdsson <> wrote on Monday, January 23, 2006 11:54 AM:


> I was wondering if anyone on the list had any suggestions on how to
> implement the following:
[...]
> 
> Traffic to and from peers via RTR_D (identified by source IP
> addresses or BGP communities) use Link A to go to and from RTR_A.
> 
> Traffic to and from peers via RTR_C (identified by a default route or
> BGP communities) use Link B for traffic to and from RTR_A.
> 
> Should either Link A or Link B go down, all traffic goes through the
> other one. 

Even though I'm not sure I understood your exact topology, MPLS Traffic
Engineering, possibly using static and/or policy-routing at the edge, is
usually a good technology to achieve this. You build two tunnels from A
to C and D, and auto-route C's next-hop to the tunnel (and likewise
towards D). Same goes for the reverse direction. No need for
policy-routing in the middle as this is done during tunnel setup. In
case your links go down, tunnel can be re-optimized over the alternate
path or can go down and you will just forward using your regular IGP..

	oli