Rockwell Automation Publication 1756-UM001M-EN-P - February 2012 189
Redundant Systems Chapter 12
EtherNet/IP Considerations
in Redundant Systems
You can have as many as seven EtherNet/IP modules in the redundant chassis.
In a redundant system, use EtherNet/IP for HMI communication or inter-
controller messaging only. HMI can communicate directly to with the primary
controller. You no longer need RSLinx Alias Topics.
ControlLogix redundancy supports EtherNet/IP for I/O control or producing
and consuming data beginning with Enhanced Redundancy System revision
19.50, and can be used for the following:
• 1715 Redundant I/O
• Remote I/O modules
• HMI connections to the primary controller
• Producing and consuming data
For information on EtherNet/IP considerations for enhanced redundant systems,
refer to the ControlLogix Enhanced Redundancy System User Manual,
publication 1756-UM535
.
IP Address Swapping
Firmware revision 13, and later, supports IP address swapping in redundant
systems. With IP address swapping, you configure the primary and secondary
EtherNet/IP modules with the same IP address. The primary EtherNet/IP
module takes the IP address; the secondary module takes that address plus one in
the last address segment.
On a switchover, the EtherNet/IP modules swap IP addresses. HMI devices
automatically continue to communicate with the new primary controller because
the IP addresses were swapped. Because of the way EtherNet/IP modules work,
during a switchover, communication between the controller and an HMI device
halts for several seconds, typically less than a minute.
For bumpless HMI connection, use either of the following:
• A dedicated ControlNet network
• A bridged connection from an EtherNet/IP network to a ControlNet
network
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