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pseudowire (l2circuit) backup-neighbor standby option

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  • 1.  pseudowire (l2circuit) backup-neighbor standby option

    Posted 08-18-2020 04:42

    Hi all,

     

    With the standby statement under the backup-neighbor hierarchy when configuring a l2circuit traffic flows over both active and backup forwarding path, but the backup-neighbor drops traffic until certain types of failover happen where the backup-neighbor becomes the active one.

    What happens if I leave the standby statement out of the configuration and the primary forwarding path fails? Does the backup-neighbor then become the active path, or is there a manual action required to get the same result?

    The reason I'm asking is because I'm using the backup-neighbor configuration after maintenance to check if the backup-neighbor path comes up after moving the local tail carrier. Should the backup path come up, all old configuration gets wiped and our standard l2circuit configuration comes into play again.

     

    Marijn



  • 2.  RE: pseudowire (l2circuit) backup-neighbor standby option

    Posted 08-18-2020 05:03

    Hello,

     


    @Beeelzebub wrote:

     

    What happens if I leave the standby statement out of the configuration and the primary forwarding path fails? Does the backup-neighbor then become the active path, or is there a manual action required to get the same result?

     


     

    If "backup-neighbor X.Y.Z.W" is configured WITHOUT standby knob, this backup PW is not pre-signaled.

    So, when active PW fails, then PW associated with that "backup-neighbor" gets LDP-signaled and traffic is moved to that PW automatically. No manual intervention is required.

    HTH

    Thx

    Alex

     

     



  • 3.  RE: pseudowire (l2circuit) backup-neighbor standby option

    Posted 08-18-2020 06:35

    Hello aarseniev,

     

    Thanks for your answer.

    Is there a reason why you would not want the backup PW to be pre-signaled by LDP?

     

    I'm configuring these back-up PWs to be sure that my configuration pre and after maintenance is correct.

    Is it still possible for the primary PW to failover to the back-up PW even if the standby knob is not configured?

     

    Marijn



  • 4.  RE: pseudowire (l2circuit) backup-neighbor standby option
    Best Answer

    Posted 08-18-2020 06:40

    Hello,

     


    @Beeelzebub wrote:

     

    Is there a reason why you would not want the backup PW to be pre-signaled by LDP?

     

     

    At least 1 - if You don't want the traffic to flow down backup standby presignaled PW. This traffic is normally dropped after reaching the egress PE but for BW preservation You may want NOT to add that "standby" knob.

     


    @Beeelzebub wrote:

     

     

    Is it still possible for the primary PW to failover to the back-up PW even if the standby knob is not configured?

     

     


     

    As I said above, the backup PW without standby gets signaled and handles traffic automatically after primary PW drops.

     

     

    HTH

    Thx

    Alex

     

     



  • 5.  RE: pseudowire (l2circuit) backup-neighbor standby option

    Posted 08-19-2020 00:37

    Great thanks. That answers my question then.

    I hope I could ask one more which is about reverting back from back-up to primary path using the revert-time knob.

     

    Juniper documentation states the following:
    "If you configure a revert time, when the configured time expires traffic is reverted to the primary path, assuming the primary path has been restored."

    Does this mean that traffic is *always* reverted back to the primary path after the revert-time has expired? Or only when the primary path has been restored?



  • 6.  RE: pseudowire (l2circuit) backup-neighbor standby option

    Posted 08-19-2020 01:13

    Hello,

    The revert happens ONLY AFTER primary PW has been restored PLUS configured revert-time.

    If primary PW is not restored, the traffic stays on backup PW and does not revert.

    HTH

    Thx

    Alex