Redundant pair on the water side of the plant, two chassis with a 1756-L73 in each, 1756-RM2 pair on fiber and a 1756-EN2T in slot 2 of both. Synchronized for four years.
The secondary's EN2T died Saturday. Put in a spare from the shelf, same catalog number, same slot, same IP. Now the RM2 in the primary shows Disqualified and the RMCT says partner mismatch, or some module compatibility thing. We swapped the RM2 fiber between the two ports, downloaded the project to the secondary again and power cycled that chassis, still disqualified.
What else is there for it to not like? Not my usual side of the plant, I'm the mechanical guy who got the weekend call. Same catalog number and the same slot, so I'm not sure what's left for the RM2 to be unhappy about.
Same catalog number isn't the same module for redundancy. What series and firmware is the spare, and what's on the EN2T in the primary? Front of the module or the Module Info tab. And which redundancy bundle exactly, the release notes list the revisions that go together.
Not sure it's series yet. Ping the new EN2T from the primary side first, then worry about that.
OG
> what series and firmware
Ping fine. Primary EN2T is series C, firmware 10.010. The spare is series D, firmware 11.002, which is what it came with in the box. Bundle is 31.052 if I'm reading the RMCT right. So they differ. Bit of progress as well, the RMCT now shows the secondary, still Disqualified though.
That's the mismatch. Redundancy needs the partner modules in matching slots at the firmware the bundle lists, and the bundle for 31 lists a specific EN2T revision, 10.010 by the look of your primary. 11.002 on the secondary is outside the bundle so the RM2 refuses to qualify, which is the right thing for it to do. Flash the spare down to 10.010 with ControlFLASH Plus, a couple of minutes over Ethernet, but check the bundle release notes first that series D is allowed at that revision, I think it is. Then in the RMCT, Synchronization tab, Synchronize Secondary. It goes Qualifying, then Synchronized. Someone did a decent article on the pairing rules: https://plctr.com/implementing-redundant-plc-systems-for-safety-critical-applications/
Release notes for 31.052 list EN2T 10.010 and say series D is fine at that revision. Flashed the spare down with ControlFLASH Plus, five minutes. RMCT, Synchronize Secondary, watched it go Qualifying for about a minute then Synchronized. Forced a switchover this morning at low demand, primary and secondary swapped clean, no bump on the pumps.
So the spare was on 11.002, the bundle wanted 10.010, and the RM2 won't take a partner that doesn't match. Flash it down, Synchronize, done.
What I've not done is check the spare RM2 in the cabinet. If that's a different revision too we'll be here again.
Thanks rsdave and billr.
Marking solved.
plctr.com team