[c-nsp] MPLS LDP Neighbourship Flapping

Aamer Akhter (aakhter) aakhter at cisco.com
Tue Nov 15 07:47:00 EST 2005


The ldp notification is decoding to 'shutdown'. Generally this means a session keepalive timeout. There was only one complete session between coming up and tear down. In that the .165 node sent the original Init, but .161 never received a followon keepalive message accepting the session. 88 seconds later, .161 tore down the session. Note that the session acceptance timer is ~90 seconds, rather than the 120 seconds when the session is fully established.

As others have already suggested, it is likely that the message is getting dropped in the path due congestion or a routing change. I did notice that you do not have qos policies configured on your core links that reserves bandwidth for multihop control protocols. Keep in mind that by default LDP packets are marked with prec 6, but unless you have configs in your core keying off of this, it will generally not help you.

If your code supports it: mpls ldp tcp pak-priority (config command, will tag the tcp packets for preferred outbound delivery on source router)

Additionally, you might want to see if a long duration ping between the loopbacks of the peers works 100% of the time. 

Please let us know what you find out, and of course open up a TAC case if it presists.

Aamer Akhter / aa at cisco.com
NSITE - cisco Systems 

> -----Original Message-----
> From: Atiqurrahman.Mohammed at relianceinfo.com 
> [mailto:Atiqurrahman.Mohammed at relianceinfo.com] 
> Sent: Monday, November 14, 2005 8:02 AM
> To: Aamer Akhter (aakhter)
> Cc: Atiqur Rahman Mohammed; cisco-nsp
> Subject: RE: [c-nsp] MPLS LDP Neighbourship Flapping
> Aamer,
>               Please find topology diagram of my network attached.
> I am also attaching the output of show tech-support from
> MCCTY1LOC1B001C76001 and MCCTY2OC1B001C76001
> (See attached file: Metro Ethernet Network Lab Setup.doc)(See attached
> file: output_debug.TXT)(See attached file: tech-support
> MCCTY1LOC1B001C76001.txt)(See attached file: tech-support
> MCCTY2LOC1B001C76001.TXT)
> Regards,
> Atiqur Rahman Mohammed
> ITIC, Reliance Infocomm
> Block J, First Floor
> Ph:303 87391
> RIM: 09324621784

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