[c-nsp] MPLS LDP Sync w/ ISIS over point to point Link

[Mikael Abrahamsson]

On Tue, 3 Feb 2015, Troy Boutso wrote:

> Getting back to my point ... If I remove the mpls ldp sync on both 
> routers the ISIS adjacency forms immediately. So this is definitely the 
> culprit. How on earth is this feature supposed to work in a production 
> environment? Am I missing something here?

I've had this problem 6-8 years ago, on XR. A router lost all its 
connectivity, and when connectivity came back the ISIS session didn't come 
up because LDP wasn't done, and LDP wouldn't come up because the loopback 
prefixes weren't reachable because ISIS wasn't up. This isn't normally how 
it should work, because ISIS should come up anyway, but with very high 
metric. This doesn't seem to be the case on all XR codebases though. What 
version are you running?

You probably have to choose between LDP session protection and "mpls ldp 
igp sync" on your code base. You can't use both it seems.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se