Ensuring Symmetrical Routing

[danieldiaz]

How do we ensure symmetrical routing between a remote-site PC accessing non-critical traffic (email) over carrier 1 and critical traffic (ERP-Application) over carrier 2 to HQ?

We are migrating from a dual-carrier hub-n-spoke Frame network (OSPF-CEF destination based session) to a dual-carrier MPLS network (OSPF-BGP)where we want to influence critical traffic over carrier one and non-critical traffic over the other while maintaining symmetrical routing.

[mchoo2005]

Are your servers in the same IP subnet? If they are, without NAT-ing, the only way I can think of is using policy-based routing.

If they are on different subnets, then another question I have is: what routing protocol do you run between your CPE (CE router) to your provider's MPLS edge (PE router)? If it's BGP, it's potentially quite straightforward: use AS_PATH prepending. Obviously you'd have to work with your MPLS providers to ensure your BGP metric will reflect on to the MPLS network as well.

HTH.

[danieldiaz]

Unfortunately, we have servers inter-mixed within the same subnet (ERP & email). We concluded the same solution, PBR.

BTW, we are running BGP between CE-PE but at the remote end it would be the same device accessing the same subnet (ERP & email) at HQ.

Thank you for the input.