Description

It was observed that VCP interfaces were flapping for VC switches QFX5120-48T / QFX5120-48Y causing disruption in the traffic towards the VC and internal fluctuations on the VC members.

Symptoms

Impact: VCP port flap causes the VC to flap and hence network interruptions.
 

Mem 0
    Xcvr 54      REV 01   740-061405   1A3CQ1A8450DT     QSFP-100G-SR4-T2
    Xcvr 55      REV 01   740-061405   1A3CQ1A8450DN     QSFP-100G-SR4-T2
Mem 1
    Xcvr 54      REV 01   740-061405   1A3CQ1A84400Z     QSFP-100G-SR4-T2
    Xcvr 55      REV 01   740-061405   1A3CQ1A84401H     QSFP-100G-SR4-T2
 
Log messages:
 

6.11.2025 23:32:10      router vccpd[9821]: VCCPD_PROTOCOL_INTF_STATE_CHANGED: Member 1, interface vcp-255/0/55.32768 came up
6.11.2025 23:32:10      router vccpd[9821]: VCCPD_PROTOCOL_INTF_STATE_CHANGED: Member 0, interface vcp-255/0/54.32768 came up
6.11.2025 23:32:10      router kernel: DEVRT_TRUNK_TABLE_CHANGE: Trunk 5: ->0/123(129,0) 0/127(128,0)
6.11.2025 23:32:10      router vccpd[9821]: VCCPD_IFL_UP: interface vcp-255/0/54 came up
6.11.2025 23:32:08      router kernel: DEVRT_TRUNK_TABLE_CHANGE: Trunk 5: 0/123(129,0) 0/127(128,0) ->
6.11.2025 23:32:08      router vccpd[9821]: VCCPD_PROTOCOL_INTF_STATE_CHANGED: Member 0, interface vcp-255/0/54.32768 went down
6.11.2025 23:32:08      router vccpd[9821]: VCCPD_PROTOCOL_INTF_STATE_CHANGED: Member 1, interface vcp-255/0/55.32768 went down
6.11.2025 23:32:08      router vccpd[9821]: VCCPD_IFL_DOWN: interface vcp-255/0/54 went down
 
 

Solution

Root Cause:
 
The CTLE Values for 100G optics was not matching with recommended values, modified the values for EEPROM from 0x55 to 0x11

As checked the fix is provided in below images per the latest PR:
Fixed Image: junos:23.2R2-S7
 

Modification History

2026-03-16 : Article Created

2026-08-02 : Updated Solution and Symptoms.