IP Address Swapping

IP address swapping enables a partnered set of communication modules that are on the same subnet to swap IP addresses during a switchover.
IMPORTANT: IP address swapping does not apply to systems that use concurrent communication, such as Logix SIS with
FLEX 5000®
 safety I/O or redundancy systems with
FLEXHA 5000™
 I/O.
The following illustration shows partnered communication modules during initial configuration.
IP Addresses During Initial Configuration
Identical assigned IP addresses for redundant communication modules
When redundant chassis operation begins, the primary communication module uses the IP address that is assigned during initial configuration. The secondary communication module automatically changes its IP address to the next highest value. When a switchover occurs, the communication modules swap IP addresses.
For example, if you assign IP address 192.168.1.3 to both communication modules, on initial system operation, the secondary
EtherNet/IP™
 communication module automatically changes its IP address to 192.168.1.4.
The following illustration shows partnered communication modules after system operation begins.
IP Addresses After System Operation Begins
Sequential IP addresses for redundant communication modules

Determine Whether to Use IP Address Swapping

Use the following table to determine whether your application requires IP address swapping.
Configuration
Required Applications
Considerations
IP address swapping
  • Remote I/O
  • Produced/consumed connections
Plan to use consecutive IP addresses for partnered communication modules. Configure the IP address, subnet mask, and gateway address for each partnered communication module with the same values. Do not assign IP addresses to communication modules outside the partnered set to values that conflict with values that are used in the partnered set.
EXAMPLE:
 The partnered set uses IP addresses 192.168.1.3 and 192.168.1.4. Use 192.168.1.5 or higher for all communication modules outside the partnered set.
Non IP address swapping
  • Your system uses concurrent communication.
  • Your system uses dynamic IP address assignments.
  • You want to minimize data server communication recovery time during a switchover.
  • Partnered set of communication modules are on different subnets.
  • If you use different subnets, you are responsible for programming your system to use the address and subnet of the new primary chassis if a switchover occurs.
If you do not use IP address swapping, plan to use two IP addresses. Assign unique IP address values for partnered communication modules. To help differentiate IP address swapping modules from other configurations, we recommend that you avoid setting the IP addresses for the partnered modules to the following format: aaa.bbb.ccc.ddd and aaa.bbb.ccc.(ddd+1).
EXAMPLE:
 The partnered set uses IP addresses 192.168.1.3 and 192.168.1.5. Use 192.168.1.6 or higher for all communication modules outside the partnered set.
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