Given this setup:
R1 and R2 are ASR9Ks running IOS-XR, and R3 is an ASR920 running IOS-XE
We have MPLS with MP-BGP running between R2 and R3 (with OSPF as the underlay in the default VRFs on those routers). Routing between R1 and R2 on the production circuit is strictly OSPF, with the protocol running in VRF3 for R2. We built a bypass link for rerouting traffic around the OSPF link with static routes for testing some things. We have no routing protocols running across the bypass link, but we do have "redistribute connected" configured in OSPF. Both of the links (the OSPF production link and bypass link) from R1 to R2 exist in the default VRF on R1 and in VRF3 on R2. There are also ports on R3 that exist in VRF3. There is no MPLS between R1 and R2.
Under normal circumstances, R1 advertises a default route to R2, which propagates it to R3 via MP-BGP and the rest of the network in VRF3. We want to be able to bypass the OSPF link between R1 and R2 for testing by using static /32 routes on both ends. On R2, the static route is in VRF3.
When we install a static route and look at the VRF3 routing table on R2, it indeed shows only one path to the destination - the /32 static we configured. When we run traces on R2 in that VRF towards the destination in the static route (westbound, beyond R1), it shows R1's side of the bypass link in the traceroutes as expected.
However, when we run traces from VRF3 on R3 to the same destination, R2 still forwards those packets across the OSPF link between R1 and R2. Since we're not redistributing the static bypass route, R3 still uses the default route to send the traffic to R2. But why, if R2 itself does have that static route and does show it to be the only path to the destination, is it sending R3's traffic through the default route path via the OSPF link?
From what I can tell, R3 is popping the label off when sending traffic towards the default route to R2. So shouldn't R2 treat it as just another packet on VRF3 and use the static route to send it across the bypass link? What is making it ignore that when receiving traffic from R3 over the MPLS link? I looked at the CEF table, and the only entry for the static destination is the static route over the bypass link, but traces from R3 to that same destination still show the OSPF link as the next-hop. What is causing R2 to forward it using the VRF3 OSPF default route instead of the static?
We did notice that redistributing that static into BGP caused R2 to forward R3's VRF3 traffic through the bypass link, but we really want to avoid redistributing those statics at all. Redistributing into BGP caused routing loops because it was being redistributed into OSPF elsewhere and propagated to R1, so R1 was just sending back to R2 and thus looping. We're trying to avoid having to do a bunch of other configuration work on R2 and other adjacent OSPF routers to prevent these loops. Seems like there should be something we can do on R2 to get it to treat R3's VRF3 traffic like any other port on R2 in that VRF, thus causing it to use the static route to send the traffic across the bypass link.
