Description

For some commits, sometimes as simple as changing an interface description, the traffic from other nodes to the local node is briefly rerouted to another path.

Please refer to PR1778841

Symptoms

  • Configuration change (commit) on a ISIS L1/L2 router which is leaking routes between L1 and L2
  • Segment Routing Global Blocks (SRGB) label range is configured globally (under protocols mpls)
  • You may notice LSP updates and even purge for LSPs generated by the ABR:
user@ABR> show isis spf log

 IS-IS level 1 SPF log:
Start time          Elapsed (secs) Count Reason
...
Thu Dec  7 15:57:14        0.021839   71 Reconfig
Thu Dec  7 15:57:14        0.025000    4 Purging LSP ABR.00-46
Thu Dec  7 15:57:17        0.019191   13 Updated LSP ABR.00-01
Thu Dec  7 15:57:22        0.024807    7 Updated LSP ABR.00-0c
Thu Dec  7 15:57:22        0.019926   14 Updated LSP ABR.00-0f
Thu Dec  7 15:57:23        0.021902    7 Updated LSP ABR.00-1c
Thu Dec  7 15:57:28        0.040558  189 Updated LSP ABR.00-22

Solution

This issue is fixed in the Junos Releases listed in  PR1778841
  
ISIS is configured on the device and whenever a commit or any operation is performed for LSP generation, a SPF is triggered. This issue is observed when global SRGB is configured and with every commit it is not reset and results on LSP getting regenerated. There is no functionality impact due to this issue, The SPF is automatically converged.


Workaround: move SRGB config to ISIS hierarchy (protocols isis source-packet-routing srgb)

Modification History

2024-01-26 : Article Created