Siemens SIMATIC NET S7-CPs Manual page 16

3 Installation and Commissioning
3.2 Module replacement without PG
General procedure
The configuration data for the CP is stored either on the CPU or on the CP. If the
data is stored on the CPU, the module can be replaced with a module of the same
type (identical order number) without a PG.
This option can be selected in the properties dialog of the CP (in the "Options" tab
− "Replace Module without PG"). We recommend that you store the configuration
data on the CPU if the configuration memory of the CPU allows.
For information on replacing previous modules, refer to the section "Compatibility"
in Chapter 7.
Module replacement: Special feature of IP address assignment from a DHCP
server
During configuration of the CP you can specify the IP configuration in the
properties dialog; one option is to obtain the IP address from a DHCP server.
Notice
When replacing modules, remember that the factory-set MAC address of the new
module is different from the previous module. When the factory-set MAC address
of the new module is sent to the DHCP server, this will return either a different or
possibly even no IP address.
Ideally, you should therefore configure IP as follows:
Always configure a client ID if you want to obtain the same IP address from the
DHCP server after replacing the module.
If you have configured a new MAC address instead of the factory-set MAC
address (generally the exception), the DHCP server always receives the
configured MAC address and the CP obtains the same IP address as the replaced
module.
B−16
CP 343-1 Lean for Industrial Ethernet / Manual Part B
C79000-G8976-C198-06
Release 09/2009