[c-nsp] LDP sessions established to non directly connected routers, when new link is activated

[CiscoNSP List]

>What do you mean by "disable ospf cost"? A link will always have a cost. If you mean you just aren't setting it manually, then it will be figured out automatically (depending on interface speed, auto-cost reference->bandwidth etc..).
>
>Sounds like you have a ring topology and tLDP session is establishing as a rLFA backup route due to equal cost paths.
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>I don't think the LDP session is causing your issue as it's a backup LSP. Probably the issue is that you are pushing traffic via your new link and for some reason it's breaking stuff. MTU mismatching would be my initial ?>thought. Make sure you have all your interface MTU's set correctly to match the underlying circuit, also that you have 'ip tcp path-mtu-discovery' configured and that you *don't* have 'no ip unreachables' configured on >your interfaces.


Cheers Dan - New link currently has a manually set hight ospf cost, so it isnt "used"...by disabling cost, I mean removing the "ip ospf cost foo" on each Int of the new link.

MTU on the new link is set identically at both ends, and can ping at that MTU...OSPF+MPLS established...although, Ive just found out that I cant "mpls ping" in one direction on the new link(Even though logs say its' established, and sh mpls ldp nei shows the neighbourship on the new circuit as "up"....so more investigations needed.

Got a TAC case open, and have a maintenance window/webex with them in ~12hours...so hopefully we can get some debug info to find the underlying cause.

Cheers for all the replies.