Fault Isolation Alarms Not Generated After Device Contact Loss

Products

• Network Observability
• Spectrum

Issue/Introduction

Fault isolation (FI) alarms are not triggered as expected when a neighbor device loses contact status․․․․​​​​​‌​

 

SYMPTOMS:

• Missing FI alarms on connections where they are expected.
• No change in behavior after neighbor device contact_status or dev_contact_status changes.
• Existing connections fail to re-evaluate neighbor status correctly.

 

 

• When all devices in a fault domain are connected to a shared media link, and the site goes down, we get no alarms.
• If one device is NOT connected to a shared media link, the fault isolation alarm will present itself on that device.

Environment

Spectrum 25.4.4

Cause

This is a defect addressed in release 25.4.4 that requires the vnmrc flag in fixed releases.

Resolution

 

1. ENABLE FAULT ISOLATION FLAG: Add the required configuration flag to the VNM resource file.

   [SpectroSERVER_Directory]/.vnmrc

   Manually add the .vnmrc flag: fix_fi_sml=true

2. RESTART SPECTROSERVER: Apply the configuration changes by restarting the server process.

3. VERIFY ALARM BEHAVIOR: 

   Randomly check one or two connections where an FI alarm was previously missing during contact loss.

    

 

Additional Information

Please note that existing connections not currently showing an FI alarm may not automatically resolve. I recommend to test this on a new set of models or a new FI domain.