Big Trouble with a little Redundency

Hi Guys

I have 2ea. 7 card Controllogix racks with
1ea 1756 L61 cpu
1ea 1756 RM redundancy module
1ea 1756 CN2R controlnet module
2ea 1756 EN2T Ethernet modules (redundant)

Controlnet going out to 3ea 12 card racks - all working fine for the time being.

Here is my dilemma - Last week we lost power and of course the batteries had not been replaced since the original construction so both Controllogixs L61s promptly lost their program.

Since this happened right at quitting time, several hours of troubleshooting trying to restore the system later - the call was made to place the 2 working Ethernet modules in the Primary Controller rack and download the program. The managed network switches were having no part of allowing it otherwise.

Of course the Secondary Ethernet module was out of the "Standby" Controller rack. Wrong address I know but the primary controller took the download and we were able to bring the system back up.

I have since placed the correct 1756 EN2T Ethernet modules back into their perspective slots and was able to associate Secondary Ethernet module to the proper rack (the standby Controller rack)

Question is what is the best way to proceed forward restoring full functionality to the system.

In the Primary Controller rack (A rack) the Standby 1756 EN2T Ethernet card is "Faulted" and I can't even plug directly in to it to correct the IP addressing. Comes up as "Ethernet Cable Unplugged"

The Standby Controller rack (B rack) has it's primary 1756 EN2T in Fault and also refuses to recognize the Ethernet connection. However the Standby 1756 EN2T is working and I can access the 1756 L61 cpu across the back plain.


This one is eating my lunch guys
Any and all thoughts and suggestions would be greatly appreciated

the easiest way would be to put the one from the rack A which is faulted to a spare slot somewhere on IO racks if you have and program. Else if you are in 192.168.1.xxx you can use the rotary switches on the EN2T. Or you could remove 1. processor 2. RM module of Chassis B and run on Chassis A (As I understand it is primary and B is not synchronised). Then you use Chassis B to make the address settings on the EN2Ts. Your communication will be still running via Chassis B EN2T module, CN2R, to the Chassis A Primary PLC.
All this of course is only if there is no way to stop the system for a while.

Hmm, Catch the knife and throw it back.

This is not a simple issue.

Two Ethernet modules in each chassis, along with your description of managed switches, suggests that this is more complex than even an ordinary ControlLogix Redundancy system.

The IP Addressing of the Ethernet modules should not have been affected by the original controller program failure in the first place; IP addresses are saved in the -EN2T onboard nonvolatile memory, but managed by the Redundancy Modules.

But of course placing the modules into the wrong slots in an attempt to "reconfigure" them... something got screwed up.

You have to take a closer look at what state the Ethernet modules you say are "faulted" are in. The RM Module Utility will probably give you some more information, as well browsing to them over the backplane from the other Ethernet module.

One more thing, did you check that "Network cable unplugged"is not because of MAC restriction in the switches?

Thanks for the replies guys - I do appreciate

Management has let me off the hook for the time being as we have a shut down scheduled in 2 weeks. At that time I'll follow the procedure listed in AB's Redundancy manual for programming and bring up the system 1 CPU at a time.

mdim - that's an interesting thought, let me get back to on that