Description

This article describes an issue where SSH access is lost after a Junos upgrade when RE1 assumes the master role.

Symptoms

1) Post Junos upgrade, SSH access is lost.

2) Console is still accessible.

3) em0 port is 'up up' on RE0 but shows physical link 'down' on RE1.

Solution

The root cause was identified as the em0 management interface being configured identically on both RE0 and RE1, but physically connected only to RE0.
 
When RE1 became the master (due to mastership switch as part of the upgrade process), its em0 interface was down due to the absence of a physical connection, resulting in loss of SSH access.
 
Customer wanted to intentionally leave the mastership on RE1, hence the Access was restored after the onsite ISP moved the management cable to RE1.
 
 
Best Practise:
Implement dual management connectivity (RE0 and RE1) to maintain uninterrupted access during failover events.
 
 

Modification History

2026-05-20 : Article Created