Rockwell Automation 1756-L6x_L7x ControlLogix System User Manual - Manual (Page 180)

180 Rockwell Automation Publication 1756-UM001O-EN-P - October 2014
Chapter 12 Redundant Systems
ControlNet Considerations
in Redundant Systems You can have as many as seven ControlNet communication modules in a
redundant chassis.
For information on ControlNet considerations for enhanced redundant systems,
see the ControlLogix Enhanced Redundancy System User Manual, publication
1756-UM535 .
EtherNet/IP Considerations
in Redundant Systems You can have as many as seven EtherNet/IP modules in the redundant chassis.
In a redundant system, you can use EtherNet/IP for HMI communication or
inter-controller messaging. 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 to produce
and consume 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,
see 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.
IMPORTANT With each ControlNet network, you must have at least two nodes external
to the redundant controller chassis to avoid timeouts on switchover.
The lowest node of each ControlNet network must be outside the
redundant controller chassis.