Redundant Controller Requirements

Follow these requirements for redundant controllers:
  • Place only one controller in the same slot in each redundant chassis.
  • Use identical series, catalog numbers, and redundancy firmware revisions for partner controllers in each redundant chassis.
  • Use the front Ethernet ports only for crossloading data between partner controllers. Do not connect them to any other devices.
  • Set the switch on the front of both controllers to the same position, such as RUN. A switch mismatch on redundant controllers affects the switchover response. See Controller Switchovers.
To size a controller, you can use the following free tools from Rockwell Automation:
All
ControlLogix®
5590 controller catalog numbers can be used as redundant controllers. However, safety partner catalog numbers 1756-L9SP and 1756-L9SPXT are not supported in Logix SIS.

Plan for Controller Communication

Controllers support a limited number of
EtherNet/IP
nodes for communication on the
EtherNet/IP
network. The maximum supported nodes vary depending on the controller catalog number. To determine the supported
EtherNet/IP
nodes for your controller, see the ControlLogix and GuardLogix Controllers Technical Data, publication 1756-TD001.
If you use the controller at or very near its connection or node limit, it can be difficult to synchronize the redundant chassis.
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