I am doing CSC with IGP/LDP between carriers.
R1 is the second level carrier.
R9 is in the backbone carrier.
R9 has a VRF interface towards R1 with MPLS enabled.
The network is 18.104.22.168/24.
Because this in a VRF, R9 creates a VPN label for 22.214.171.124 and advertises it to the other PEs.
However, when the R1/R9 LDP session comes up, R9 sends this same label to R1!
R1 then uses this label (I believe erroneously) when sending LDP/TCP keepalives to R9. R9 pops the label off and forwards the packet back out the interface (following the LFIB). R1 then sends it right back! Eventually the LDP session dies because the keepalives are never processed locally by R9. The LFIB flushes, LDP comes back up and the whole thing starts again.
The workaround I have in place is to deny labels for the directly network (126.96.36.199/24) on R1 when received from R9. This works great and things are stable. However, I want to know if there is something else I am missing here.
What is the underlying issue?
Have I misconfigured something?
Is this a bug?
Is this by design?