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

[CiscoNSP List]

Hi Everyone,



Bit of a strange one.



2 x ASR1001's (ASR1 and ASR2) directly connected (POPA), with OSPF, MPLS and BGP established



ASR1 connects to POPB (ME36001), also with OSPF, MPLS and BGP established



ME36001 connects to ME36002 at POPB, also with OSPF, MPLS and BGP established



ME36002 connects to an ASR1006 at POPC, also with OSPF, MPLS and BGP established



We have a new link connecting to ASR2(POPA) that goes to POPD, also with OSPF, MPLS and BGP established - but OSPF cost set high so that it is not used...due to a strange outage it causes when OSPF is set to no cost.



As soon as the new link on ASR2(POPA) and ASR1006(POPD) OSPF is set to no cost, ASR2(POPA) for some reason establishes LDP to ME36002(POPC) - but it has no direct connection to this device, nor is targetted LDP enabled to this device, and ASR1(POPA) establishes LDP to ASR1006(POPC) - but it also has no direct connection to this device, nor is targetted LDP enabled to this device....result of these LDP sessions establishing is ASR1(POPA) losing BGP neighbourships to three other routers that are connected via the ASR1006(POPC).



Ive opened a TAC case, but if anyone can explain how/why the LDP sessions would establish when this new link is "activated" it would be greatly appreciated!



Cheers.