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[ACX] Primary LSP is up and Secondary Standby LSP is down

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Article ID: KB35643 KB Last Updated: 22 May 2020Version: 1.0
Summary:

Secondary standby LSP is down due to the error, 'CSPF: Can't find non-overlapping path'.

Cause:

Primary and secondary standby LSP are using the same exit interface.

Solution:

When the primary and secondary standby LSP are using the same exit interface, secondary standby LSP remains down. It gives a computation error for the secondary standby LSP. 

user@router# show protocols mpls 
label-switched-path R1-R5 {
    from 1.1.1.1;
    to 5.5.5.5;
    inter-domain;
    primary R3;
    secondary test {
        standby;
    }
}
path R3 {
    3.3.3.3;
}
path test {
    3.3.3.3;
}
interface ge-0/0/1.0;
interface ge-0/0/2.0;

[edit]
user@router# run show mpls lsp extensive 
Ingress LSP: 1 sessions

5.5.5.5
  From: 1.1.1.1, State: Up, ActiveRoute: 0, LSPname: R1-R5
  ActivePath: R3 (primary)
  PathDomain: Inter-domain
  LSPtype: Static Configured, Penultimate hop popping
  LoadBalance: Random
  Encoding type: Packet, Switching type: Packet, GPID: IPv4
*Primary   R3               State: Up
    Priorities: 7 0
    SmartOptimizeTimer: 180
    Computed ERO (S [L] denotes strict [loose] hops): (CSPF metric: 10)
13.13.0.2 S 
    Received RRO (ProtectionFlag 1=Available 2=InUse 4=B/W 8=Node 10=SoftPreempt 20=Node-ID):
          13.13.0.2 35.35.0.2
   17 Mar 30 04:18:47.318 Self-ping ended successfully
   16 Mar 30 04:18:46.839 Record Route:  13.13.0.2 35.35.0.2
   15 Mar 30 04:18:46.839 Up
   14 Mar 30 04:18:46.839 Self-ping started
   13 Mar 30 04:18:46.839 Self-ping enqueued
   12 Mar 30 04:18:46.511 Originate Call
   11 Mar 30 04:18:46.511 CSPF: computation result accepted  13.13.0.2
   10 Mar 30 04:18:46.508 Clear Call
    9 Mar 30 00:36:14.072 Self-ping ended successfully
    8 Mar 30 00:36:13.638 Selected as active path
    7 Mar 30 00:36:13.623 Record Route:  13.13.0.2 35.35.0.2
    6 Mar 30 00:36:13.623 Up
    5 Mar 30 00:36:13.622 Self-ping started
    4 Mar 30 00:36:13.622 Self-ping enqueued
    3 Mar 30 00:36:13.280 Originate Call
    2 Mar 30 00:36:13.280 CSPF: computation result accepted  13.13.0.2
    1 Mar 30 00:33:15.156 CSPF failed: no route toward 5.5.5.5[6 times]
  Standby   test             State: Dn
    Priorities: 7 0
    SmartOptimizeTimer: 180
        No computed ERO.
    1 Mar 30 04:55:48.186 CSPF: Can't find non-overlapping path to 3.3.3.3[57 times]
  Created: Mon Mar 30 00:29:50 2020     
Total 1 displayed, Up 1, Down 0


Deactivating primary LSP:

[edit]
user@router# deactivate protocols mpls label-switched-path R1-R5 primary R3  

[edit]
user@router# commit 
commit complete


Once primary LSP is deactivated, secondary LSP is UP.

user@router# run show mpls lsp extensive 
Ingress LSP: 1 sessions

5.5.5.5
  From: 1.1.1.1, State: Up, ActiveRoute: 0, LSPname: R1-R5
  ActivePath: test (secondary)
  PathDomain: Inter-domain
  LSPtype: Static Configured, Penultimate hop popping
  LoadBalance: Random
  Encoding type: Packet, Switching type: Packet, GPID: IPv4
*Standby   test             State: Up
    Priorities: 7 0
    SmartOptimizeTimer: 180
    Computed ERO (S [L] denotes strict [loose] hops): (CSPF metric: 10)
13.13.0.2 S 
    Received RRO (ProtectionFlag 1=Available 2=InUse 4=B/W 8=Node 10=SoftPreempt 20=Node-ID):
          13.13.0.2 35.35.0.2
    9 Mar 30 04:57:36.516 Self-ping ended successfully
    8 Mar 30 04:57:35.887 Selected as active path
    7 Mar 30 04:57:35.871 Record Route:  13.13.0.2 35.35.0.2
    6 Mar 30 04:57:35.871 Up
    5 Mar 30 04:57:35.871 Self-ping started
    4 Mar 30 04:57:35.871 Self-ping enqueued
    3 Mar 30 04:57:35.691 Originate Call
    2 Mar 30 04:57:35.691 CSPF: computation result accepted  13.13.0.2
    1 Mar 30 04:57:14.800 CSPF: Can't find non-overlapping path to 3.3.3.3[60 times]
  Created: Mon Mar 30 00:29:50 2020


Once the exit interface of Primary and Secondary LSP is different, Secondary standby is UP again.

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