Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 28)

28 Rockwell Automation Publication 1715-UM001C-EN-P - March 2014
Chapter 1 Redundancy System Overview
Obtaining a New IP Address
The primary module’s IP address is stored in the adapter base unit through
interaction with the TCP/IP object. If a stored primary IP address is available,
the adapter uses that address. If a stored primary IP address is not available, then
the adapter uses BOOTP/DHCP to obtain an IP address.
The adapter transmits DHCP requests, but is able to process a BOOTP/DHCP
response from either a DHCP or BOOTP server. If the BOOTP/DHCP
request is unsuccessful, the secondary adapter module (that is, Module B),
attempts to obtain the primary module’s IP address through BOOTP/DHCP.
The adapters continue to attempt BOOTP/DHCP configuration until an IP
address is obtained, alternating between adapter Modules A and B. Once an
adapter module has obtained the IP address, the secondary module can use that
IP address + 1.
Once an adapter has a primary IP address, it confirms that it does not have a
duplicate IP address. See EtherNet/IP Modules in Logix5000 Control Systems,
publication ENET-UM001 . Duplicated IP addresses are displayed by the
Network Status indicator showing solid RED.
For additional information about assigning an IP address for the first time, see
Chapter 2, Assign an IP Address on page 111 .