Does adding node-link protection cause LSP to flap?

‎11-05-2016 06:59 AM



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?

Accepted by topic author
‎11-06-2016 11:41 AM

Re: Does adding node-link protection cause LSP to flap?

‎11-06-2016 05:49 AM

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.

Steve Puluka BSEET - Juniper Ambassador
IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)

Re: Does adding node-link protection cause LSP to flap?

‎11-06-2016 11:41 AM

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


Re: Does adding node-link protection cause LSP to flap?

‎11-06-2016 12:49 PM



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




Re: Does adding node-link protection cause LSP to flap?

‎11-20-2016 11:12 AM



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.