Here's the scenario:
I have two main sites with a route to a remote network (over point to point T1's) and I have two other branches that need to access that network. All four of these sites are connected over an MPLS network. Both main sites are advertising a route to the remote network using eBGP. I need one of the branches to route through main site 1 and the other to route through main site 2. At the same time, I would like to have a secondary route for each of the branches in case one of the main sites goes down.
Well this is what I've got, can you tell me what we're doing wrong? We want router C to go out router B to access the host and router D to go out router A to access the host. Additionally, we would like the option of failing over to A or B respectively, if one of them should go down.
If I add the line "network 10.46.0.56 mask 255.255.255.255" to router B, then router D starts routing to router B instead of to router A which it is doing now.
Please note that we have two links to the MPLS network from router A and that we're using eBGP multihop to load balance those circuits. I've also cleared out the WAN addressing and renamed a few other things for privacy reasons.
Thanks in advance for your help.
I don't think I have an answer you will like, though I hope it will be helpful in some way.
I don't think they are BSing you. BGP sounds like it is working as designed and implemented.
It's true, you are using eBGP and your configuration makes sense. But ATT, and indeed most providers will be using eBGP toward their MPLS VPN customers, and iBGP or a mix of eBGP and iBGP in their core network. When an update gets to a BGP router, it will make a decision which path is the best path based on algorithm + policy (like your route-maps) and it is that best path that is sent to peers. This process is followed across both AT&T and your BGP routers. The default is to select a single best path.
This single best path behavior can be modified. Three such featurs are iBGP Multipath, eBGP Multipath, and eiBGP Multipath. These feature allows the BGP router to select more than one "equal" best path. However, such features may break or adversely affect AT&Ts core in some fashion that you and I will never have visibility to.
So, in my opinion, it sounds like they cannot or will not modify their network for your use-case. The problem you are facing is not necessarily a technical problem on your end, but is likely a technical, a policy, a business ($$) or an implementation problem from AT&T. And while a say problem, I don't mean broken, but rather a problem for you.