Allen-Bradley 193-DNENCAT, User Manual, Page: 26 / 112

26 Rockwell Automation Publication 193-UM014C-EN-P - August 2016
Chapter 2 Configure the EtherNet/IP Communication Auxiliary Module
module. In this case, disconnect the uplink to set the address and configure the
module to retain its static address before reconnecting to the uplink. This is
not a problem if you have node names configured in the module and leave
DHCP enabled.
Duplicate IP Address
Detection
When you change the IP address or connect the module to an EtherNet/IP
network, the module checks to make sure that the IP address assigned to this
module does not match the address of any other network device. If the module
determines that another device on the network with a matching IP address, the
EtherNet/IP port of the module goes into conflict mode where the Network
Status LED indicator is solid red.
To resolve this conflict, use the instructions below to change the IP address of
the module. Then, cycle power to the module or reset the modules by
disconnecting and then reconnecting the Ethernet cable.
Two modules could possibly detect a conflict simultaneously. If this occurs,
perform this procedure.
1. Remove the module with the incorrect IP address and correct its
conflict.
2. Cycle power or disconnect the Ethernet cable from the second module
and reconnect it.
Behavior of Modules With Duplicate IP Addresses
Devices in conflict over an IP address behave differently depending on whether
connections have been established to either of the modules and whether both
modules support duplicate IP address detection.
Table 4 - Device Conflict over Duplicate IP Addresses
ATTENTION: The EtherNet/IP Communication Auxiliary module must be
assigned a fixed network address. The IP address of this module
must not
be dynamically provided. Failure to observe this precaution may result in
unintended machine motion or loss of process control.
If then
Both modules support duplicate IP address
detection,
The first started module uses and retains its IP address.
The other module detects a conflict, gives up the IP address, and
enters conflict mode.
Both modules support duplicate IP address
detection and are started at roughly the same
time,
One of the modules surrenders the IP address and enters 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 first obtains the IP address.
The module that supports duplicate IP address detection detects
the conflict and gives up the IP address.