Description

We have a strange behaviour with link-degrade-monitoring on 400G interfaces. The "set" threshold is converted from 1e-6 to 1e-5.

Symptoms

Config:
set interfaces et-0/0/0 link-degrade-monitor link-degrade-monitor-enable
set interfaces et-0/0/0 link-degrade-monitor actions media-based
set interfaces et-0/0/0 link-degrade-monitor recovery manual
set interfaces et-0/0/0 link-degrade-monitor thresholds set 1e-6
set interfaces et-0/0/0 link-degrade-monitor thresholds warning-set 1e-8
set interfaces et-0/0/0 link-degrade-monitor thresholds warning-clear 1e-10
set interfaces et-0/0/0 link-degrade-monitor thresholds interval 100


user@router> show interfaces extensive et-0/0/0
Physical interface: et-0/0/0, Enabled, Physical link is Up
...
  Link Degrade :
    Link Monitoring                   :  Enable
    Link Degrade Set Threshold        :  1E-5       <<<<
    Link Degrade Clear Threshold      :  1E-10
    Link Degrade War Set Threshold    :  1E-8
    Link Degrade War Clear Threshold  :  1E-10
    Estimated BER                     :  1E-10
 

Solution

  
On all Junos Evolved platforms, if SET threshold was within valid range and CLEAR value is out of range, software was resetting both SET and CLEAR to default thresholds, which is incorrect.
In this case, only CLEAR should have been set to default values and SET thresholds must be using configured values. Due to which the threshold vales will get reprogrammed due to a software bug and the results will give different value than what the user had configured.
The same issue is seen if CLEAR thresholds were in range and SET thresholds were out of range.

Workaround: configure "SET/CLEAR" threshold explicitly.

Issue is fixed in the below JUNOS releases:

22.2R3-S4-EVO
24.1R1-EVO
23.4R2-EVO
23.2R2-EVO
 

Modification History

2023-12-27 : Article Created