User manual

Hot Standby
33002479 06 07/2008 315
IP Address
Transparency
When a switchover occurs, a new primary CPU PLC takes the IP address of the old
primary CPU PLC. When the PLC that has stopped becomes operational again and
rejoins the hot standby system, it takes the IP address of the secondary PLC. A new
primary CPU NOE must have the same IP address as the former primary CPU NOE.
The IP address in the secondary NOE (an NOE in the secondary state) is IP address
+ 1.
The NOEs integrated into the Modicon Quantum Hot Standby with Unity
configuration coordinate this swapping IP address with the management of Ethernet
services used.
UNINTENDED EQUIPMENT OPERATION
For a Quantum Hot Standby configuration:
z Do not use the address IP + 1.
z Do not use consecutive IP addresses of the configured IP address.
z Do not configure the primary CPU address as nnn.nnn.nnn.254. This causes
the standby CPU IP address to be: nnn.nnn.nnn.255. The module would then
return the diagnostic code Bad IP configuration.
Failure to follow these instructions can result in injury or equipment damage.
CAUTION