Multiple MPLS Carriers/Networks

Question

Does anyone have any experience with using 2 MPLS carriers for load balancing. We'd like to have a primary MPLS network with ATT and then a backup MPLS network with MCI. But rather than use MCI strictly for backup we'd like to load balance traffic across both networks. Most of our bigger sites will have a connection into both clouds. Anyone have any idea how we'd handle the routing for that?

Answer 1

I assist in supporting an environment which might almost be identical to that you want to move into.
The first issue you might bump into is the way EBGP will prefer to always use its CE-PE link if it sees otherwise equal paths. Simple solution, divide your traffic to your CEs. We do this either by using GLBP for small sites, or via equal cost paths within the LANs routing topology to the CE routers.
Second issue you might bump into is if the AS topologies are different between the MPLS providers making AS hop counts different between sites. We addressed this issue by defining and maintaining our own logical topology that looks identical between the different MPLS providers.
Both of the prior principally perform static load balancing but if you working with 12.4 or later, you might also want to look at OER. It can dynamically load balance, either with the static techniques, above, or without them.
PS:
We also deal with the situation where two sites are not on the same provider's MPLS. (Usually the result of some problem.) For this, we leak routes between the providers at major hubs permitting traffic to transit between the providers for sites that can not be reached on the same provider.