Hi Mike, sorry...just a question: NonStop Switching redudancy mode (if active <-- where Configured Mode = Current Mode) doesn't admit that MM1 and MM2 run with mismatched software versions...that's just to say...if the NonStop Switching redudancy mode is just enabled the valid scenario falls into the case described with this TAC statement:
...when the software in active and standby MM are same during redundancy switchover after switching to standby only the active MM will reboot and the ping is continuous with no drops in L2 and L3 (This is a condition that happens during failover)...
So, just to be clear, wasn't really your system in NonStop Switching redudancy mode (so it was really in Warm Standby)?
What I mean is...did you started your upgrade journey with an Aruba 5406R zl2 switch where its "redudancy status" was similar to (software versions listed are those of my system, YMMV):
5412Rzl2# show redundancy
Configured Mode: Nonstop Switching
Current Mode : Nonstop Switching
Rapid Switchover Stale Timer : 90
Failovers : 2
Last Failover : Wed May 16 11:57:53 2018
Slot Module Description State SW Version Boot Image
---- ---------------------------------------- -------- ------------- ----------
MM1 HP J9827A Management Module 5400Rzl2 Active KB.16.05.0007 Primary
MM2 HP J9827A Management Module 5400Rzl2 Standby KB.16.05.0007 Primary
5412Rzl2# show redundancy detail
Slot Role Module Up Since State Since State
---- -------- ------------------- ------------------- -----------------
MM1 Active 05/16/18 14:41:30 05/16/18 14:48:53 Active
MM2 Standby 05/16/18 14:49:26 05/16/18 14:50:47 Standby
Failover Log:
Slot Role Time Reason
---- -------- ------------------- ---------------
MM2 Active 05/16/18 11:57:52 Switchover
MM1 Active 05/16/18 11:50:09 Switchover
5412Rzl2# show flash
Image Size (bytes) Date Version
----------------- ------------ -------- --------------
Primary Image : 33511892 03/27/18 KB.16.05.0007
Secondary Image : 33511892 03/27/18 KB.16.05.0007
Boot ROM Version
----------------
Primary Boot ROM Version : KB.16.01.0006
Secondary Boot ROM Version : KB.16.01.0006
Default Boot Image : Primary
Default Boot ROM : Primary
5412Rzl2# show version
Management Module 1: Active
Image stamp: /ws/swbuildm/rel_venice_qaoff/code/build/bom(swbuildm_rel_venice_qaoff_rel_venice)
Mar 26 2018 23:16:09
KB.16.05.0007
847
Boot Image: Primary
Boot ROM Version: KB.16.01.0006
Active Boot ROM: Primary
Management Module 2: Standby
Image stamp: /ws/swbuildm/rel_venice_qaoff/code/build/bom(swbuildm_rel_venice_qaoff_rel_venice)
Mar 26 2018 23:16:09
KB.16.05.0007
847
Boot Image: Primary
Or what else?
Apart from what TAC wrote you (which is usually found on any ArubaOS-Switch guides) also this (old) article looks interesting to read.