We have a system with Redundant Allen Bradley ControlLogix 1756-L82E PLCs linked with the 1756-RM2 redundancy module. I am having issues with trying to come up with the correct Port Segment Path for the Rockwell Driver. I assume with the redundant PLCs, you reference the redundancy module for tag information and allow them to route the message to the primary PLC.

For anyone who may be interested, we found the solution to this issue. The correct value for the Port Segment Path for our setup was [1,1][1,0]. As always, the ControlLogix processor was in Slot 0, the Redundancy Module was in Slot 1 and the EN2T module was in Slot 2. Therefore, the first set of numbers sends the ethernet packet to the backplane then to Slot 1 (RM2 Module) the second set of numbers sends it from the Redundancy module, to the backplane then to the processor in Slot 0.

We are only using one Port Tag and no drive multiplexer as the Redundancy Modules take care of the routing to the primary processor for you. Both EN2T modules are set on the same IP address, however, with Redundancy turned on, the secondary EN2T module will have Primary IP Address + 1 (i.e. Primary IP xxx.xxx.xxx.100 the Secondary IP is xxx.xxx.xxx.101). In FactoryTalk Linx, the Secondary EN2T Module will show up as xxx.xxx.xxx.101(xxx.xxx.xxx.100). As soon as the primary processor fails, the secondary EN2T module will assume the IP address of the primary and the primary will change to the secondary.

We failed the primary controller (shut power off) and the secondary picked up immediately with no failure in VTScada.