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  • 1.  Does adding node-link protection cause LSP to flap?

    Posted 11-05-2016 07:00



    Just a quick question if anyone could advise:


    Does the act of commiting a change to add node-link protection to an existing LSP cause it to flap/rebuild?


  • 2.  RE: Does adding node-link protection cause LSP to flap?
    Best Answer

    Posted 11-06-2016 05:49

    I don't know the answer but how to find out.


    On the device in question, apply the new setting to the LSP on the candidate config.

    Do a show | compare

    If the lsp shows a minus sign - for the config followed by a + sign with all the existing and the new setting.  The LSP will bounce.  This is showing that the LSP is removed and replaced by the full config with the new setting.


    If the only line is the + to add the new settting line, then the LSP stays up and the new setting is simply added.


    You can then rollback to the current and do the actual update at the desired time.

  • 3.  RE: Does adding node-link protection cause LSP to flap?

    Posted 11-06-2016 11:42

    Thank you, that's really useful for future reference - much appreciated

  • 4.  RE: Does adding node-link protection cause LSP to flap?

    Posted 11-06-2016 12:50



    I believe the LSP is rebuilt as the RSVP session gets recreated due to new flags in the RSVP PATH msg:

    root@P1# show | compare
    [edit protocols mpls label-switched-path P1-P2]
    +    node-link-protection;
    root@P1# commit
    Nov 06 20:48:27
    commit complete

    root@P1# run show mpls lsp name P1-P2 extensive | no-more
    Nov 06 20:48:38
    Ingress LSP: 3 sessions
    From:, State: Up, ActiveRoute: 0, LSPname: P1-P2
    ActivePath: (primary)
    Node/Link protection desired
    LSPtype: Static Configured, Penultimate hop popping
    LoadBalance: Random
    Encoding type: Packet, Switching type: Packet, GPID: IPv4
    *Primary State: Up
    Priorities: 7 0
    OptimizeTimer: 1800
    SmartOptimizeTimer: 180
    Reoptimization in 1770 second(s).
    Computed ERO (S [L] denotes strict [loose] hops): (CSPF metric: 100) S
    Received RRO (ProtectionFlag 1=Available 2=InUse 4=B/W 8=Node 10=SoftPreempt 20=Node-ID):
    6 Nov 6 20:48:37.271 Link-protection Up
    5 Nov 6 20:48:28.306 Selected as active path
    4 Nov 6 20:48:28.294 Record Route:
    3 Nov 6 20:48:28.294 Up
    2 Nov 6 20:48:28.250 Originate Call
    1 Nov 6 20:48:28.250 CSPF: computation result accepted
    Created: Sun Nov 6 20:48:28 2016
    Total 1 displayed, Up 1, Down 0

    root@P1# run show rsvp session name P1-P2 extensive | no-more
    Nov 06 20:48:49
    Ingress RSVP: 4 sessions
    From:, LSPstate: Up, ActiveRoute: 0
    LSPname: P1-P2, LSPpath: Primary
    LSPtype: Static Configured
    Suggested label received: -, Suggested label sent: -
    Recovery label received: -, Recovery label sent: 0
    Resv style: 1 SE, Label in: -, Label out: 0
    Time left: -, Since: Sun Nov 6 20:48:28 2016
    Tspec: rate 0bps size 0bps peak Infbps m 20 M 1500
    Port number: sender 1 receiver 35667 protocol 0
    Node/Link protection desired
    Type: Link protected LSP, using Bypass->
    1 Nov 6 20:48:37 Link protection up, using Bypass->
    PATH rcvfrom: localclient
    Adspec: sent MTU 1500
    Path MTU: received 1500
    PATH sentto: (ge-0/0/1.0) 3 pkts
    RESV rcvfrom: (ge-0/0/1.0) 3 pkts, Entropy label: Yes
    Explct route:
    Record route: <self> (node-id)
    Total 1 displayed, Up 1, Down 0



  • 5.  RE: Does adding node-link protection cause LSP to flap?

    Posted 11-20-2016 11:12



    To be precise, the flap can be avoided if the LSP is configured as 'adaptive' :

    set protocols mpls label-switched-path xxx adaptive

    Although a new rsvp session is created, this happens in a make-before-break mode, hence the LSP does not flap.