Rockwell Automation 1768-EWEB EtherNet/IP Web Server Module User Manual - Manual (Page 42)

Publication ENET-UM527E-EN-P - October 2006
42 Configure a Network Address For a Web Server Module
Duplicate Detection Scenarios
The behavior of devices that are in conflict over an IP address varies,
depending on whether connections have been established to either of
the modules and whether both modules support duplicate IP address
detection.
IP Address Swapping 1756-EWEB modules with firmware revision 2.2 or later support IP
address swapping.
During a switchover in ControlLogix redundancy systems, these
modules swap their IP addresses with their partner modules in the
other redundant chassis.
For more information about IP address swapping, see the
ControlLogix Redundancy User Manual, publication 1756-UM523.
DNS Addressing To further qualify an address of a module, you can use DNS
addressing to specify a host name for a module, which also includes
specifying a domain name and DNS servers. DNS addressing lets you
set up similar network structures and IP address sequences under
different domains.
DNS addressing is necessary only if you refer to the module by host
name and use the web server module to initiate MSG instructions out
of the web server module to another device.
To use DNS addressing, you must:
1. Assign a host name to the module.
If Then
Both modules support duplicate IP address
detection The module that powers up first and uses
the IP address keeps the IP address. The
other module will detect a conflict, give up
the IP address, and enter conflict mode.
Both modules support duplicate IP address
detection and both modules power up at
roughly the same time Both modules give up the IP address and
enter conflict mode.
One module supports duplicate IP address
detection and a second module does not the second module generally keeps its IP
address, regardless of which module
obtains the IP address first. The module that
supports duplicate IP address detection will
detect the conflict and give up the IP
address.