Description

This KB explains the working of SmartOptimizeTimer in flapping link scenarios

Symptoms

Customer might observe that RSVP LSP is not re-optimizing as per SmartOptimizeTimer


for example.


1st Flap - Link came up on 18:06 & re-optimization done at 18:09 – 3min (expected)

2nd Flap - Link came up on 18:16 but path switching happened on 18:41 (25min) (Unexpected

Solution

In this issue we observed that

 

1st Flap - Link came up on 18:06 & re-optimization done on 18:09 – 3min (expected)

2nd Flap - Link came up on 18:16 but path switching happened on 18:41 (25min) (Unexpected)

 

as per configuration, OptimizeTimer is 3600 I.e 1 hr and SmartOptimizeTimer is 180 (5 min).

 

as mentioned on below document,

 

https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/statement/smart-optimize-timer-edit-protocols-mpls.html

 

Sometimes after the smart optimizer causes the LSP to be placed back on its primary path, the primary path goes down again within 60 minutes. When this happens, the smart-optimize-timer is disabled automatically, and the

optimize-timer (regular path optimization) goes into effect. This is to protect against a flapping link being used.

 

so after second flap, reoptimizer timer fallback from smart-optimze-timer to optimize timer which can be at any point in countdown timer of optimise time.

Modification History

2026-01-10 : Article Created