Routing

Hi,

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?

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.

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

Hi, 

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

[edit]
root@P1# run show mpls lsp name P1-P2 extensive | no-more
Nov 06 20:48:38
Ingress LSP: 3 sessions

192.168.0.2
 From: 192.168.0.1, 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)
 10.0.0.1 S
 Received RRO (ProtectionFlag 1=Available 2=InUse 4=B/W 8=Node 10=SoftPreempt 20=Node-ID):
 192.168.0.2(flag=0x20) 10.0.0.1(Label=0)
 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: 192.168.0.2(flag=0x20) 10.0.0.1(Label=0)
 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 10.0.0.1
 Created: Sun Nov 6 20:48:28 2016
Total 1 displayed, Up 1, Down 0

[edit]
root@P1# run show rsvp session name P1-P2 extensive | no-more
Nov 06 20:48:49
Ingress RSVP: 4 sessions

192.168.0.2
 From: 192.168.0.1, 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->10.0.0.1
 1 Nov 6 20:48:37 Link protection up, using Bypass->10.0.0.1
 PATH rcvfrom: localclient
 Adspec: sent MTU 1500
 Path MTU: received 1500
 PATH sentto: 10.0.0.1 (ge-0/0/1.0) 3 pkts
 RESV rcvfrom: 10.0.0.1 (ge-0/0/1.0) 3 pkts, Entropy label: Yes
 Explct route: 10.0.0.1
 Record route: <self> 192.168.0.2 (node-id) 10.0.0.1
Total 1 displayed, Up 1, Down 0

Cheers,

Ashvin

Hi,

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.

Cheers,

Ashvin