Unanswered Question
Sep 7th, 2009
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I would like to know exactly NNHOP protection in MPLS core.

first of all, Please check the attached file.

Regard the attached file. when the R4 fail, the R2 activate the FRR NNHOP protection through R3.

the most thing that I want to know is that How R2 know the label 36? the label is local siginificanly so R2 doesn't know the label 36.

when NNHOP is activated, the R2 is pushed 25/36 ? in other protocol RSVP?

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Laurent Aubert Tue, 09/08/2009 - 05:03
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As soon as FRR is enabled on the head-end, it turns on a flag called "Label recording" in the SESSION_ATTRIBUTE object of the PATH message so in the RESV message, each node will record its label in a RECORD_ROUTE object.

This is how your PLR is aware of the label expected by the NNHOP.



amit.bhagat Tue, 09/08/2009 - 17:11
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When you enable NNHOP using

tunnel mpls traffic-eng fast-reroute node-protect command under TE tunnel configuration on the PLR, it sets the flag to 0x10 in the RSVP PATH messages.

This causes the MP to send the label in the sub-object of the RRO object in the RSVP RESV message.




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