Hello everyone, I have two ControlLogix racks, each equipped with the following components: - 1 x 1756-L61 CPU - 1 x 1756-RM Redundancy Module - 1 x 1756-CN2R ControlNet Module - 2 x 1756-EN2T Ethernet Modules (configured for redundancy). Currently, the ControlNet connects to three 12-card racks, and everything is functioning correctly at the moment. However, I've encountered a significant issue. Last week, we experienced a power outage, and unfortunately, the batteries had not been replaced since the original installation. As a result, both ControlLogix L61 CPUs lost their programs. This incident occurred right before quitting time, leading to several frustrating hours of troubleshooting to restore the system. Eventually, we decided to install the two operational Ethernet modules into the Primary Controller rack and download the existing program, as the managed network switches were preventing other connections. While the Secondary Ethernet module was removed from the Standby Controller rack, I understand that the address was incorrect. Nevertheless, the Primary Controller accepted the download, and we managed to bring the system back online. I've since reinstalled the correct 1756-EN2T Ethernet modules back into their original slots and successfully associated the Secondary Ethernet module with its designated Standby Controller rack. Now, I need guidance on how to fully restore the system's functionality. In the Primary Controller rack (Rack A), the Standby 1756-EN2T Ethernet card is displaying a "Fault" status, and I'm unable to connect directly to it for IP address correction, as it shows "Ethernet Cable Unplugged." Meanwhile, Rack B's primary 1756-EN2T is also faulted and does not recognize the Ethernet connection. However, the Standby 1756-EN2T is operational, and I can access the 1756-L61 CPU through the backplane. I'm looking for your insights and recommendations on how to effectively resolve these issues. Any thoughts would be immensely appreciated. Thank you!
The simplest solution is to transfer the faulty module from Rack A to an available spare slot in your IO racks, assuming you have one and the necessary programming capabilities. If you're connected to the IP range 192.168.1.xxx, you can adjust the settings using the rotary switches on the EN2T module. Alternatively, you can remove the following components from Chassis B: 1. the processor, and 2. the RM module, and then install them into Chassis A, which functions as the primary unit (while Chassis B remains unsynchronized). Afterward, configure the address settings on the EN2Ts using Chassis B. This way, communication will continue through the Chassis B EN2T module and CN2R, directing data to the primary PLC in Chassis A. Note that this process is only advisable if you cannot afford to stop the system temporarily.
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This situation is quite intricate. The presence of two Ethernet modules within each chassis, coupled with your mention of managed switches, indicates a complexity that goes beyond a standard ControlLogix Redundancy system. Ideally, the IP addressing for the Ethernet modules should remain unaffected by the initial failure of the controller program; IP addresses are stored in the non-volatile memory of the EN2T modules and are managed through the Redundancy Modules. However, it appears that incorrectly placing the modules in their slots during an attempt to "reconfigure" could have led to complications. It's crucial to examine the condition of the Ethernet modules you describe as "faulted." Utilizing the RM Module Utility may provide further insights, and accessing them via the backplane from the other Ethernet module could also yield valuable information. By carefully investigating these elements, you'll be better equipped to resolve the issues at hand.
Additionally, have you verified that the "Network cable unplugged" issue isn't due to MAC address restrictions on the switches? It's essential to ensure that there are no limitations on the MAC addresses, as this could affect your network connectivity.
Thank you all for your feedback—I truly appreciate it! Management has granted me some relief for now since we have a shutdown planned in two weeks. During that time, I will adhere to the procedures outlined in AB's Redundancy Manual regarding programming, and I’ll bring the system back online one CPU at a time. Mdim, that’s an intriguing idea; I’ll circle back to you on that.
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