MTR - Multi Topology Routing to control Load Sharing traffic in WAN

Sometimes my customers (especially large enterprise or oil companies) ask me if it is possible to route different traffic via different physical links. Usually they ask this question in order to load share the traffic via multiple physical links. This makes sense, since bandwidth is very expensive in Indonesia, and by controlling traffic, they can make good use of the backup links for less critical traffic.

There are several alternatives to solve this problem. In the old days, we could use policy routing, but it is cumbersome and (for some small routers) it is CPU intensive, we have to find different way...

Multi Topology Routing
Multi Topology Routing introduced by Cisco to allow one physical network topology to support many logical topology that is used by different applications. Refer to the figure below :

This is an example where one physical (base) network can support three different applications (voice, multicast and video) in three different logical topology.

MTR (Multi Topology Routing) is configured using router address family configuration command under the following routing protocol : BGP, EIGRP, IS-IS, and OSPF.

Other Alternatives
Other alternatives is MPLS TE (Traffic Engineering), which also capable to control traffic similar to MTR. However MPLS TE requires MPLS to be configured in the network, and it does require large/jumbo frame support to accommodate MPLS label overhead. And not every data link layer support this... (anyway, if you're interested, may be next time I'll post an article re MPLS TE).