Siemens SIMATIC S7-1500 System Manual page 198

Configuration
8.2 Configuring R/H CPUs
Redundancy IDs
In the STEP 7 project tree, each of the two CPUs is displayed with its own tree in the
redundant system:
Figure 8-3 Redundant system in the project tree
Each CPU of the redundant system has a redundancy ID. The redundancy ID is used to assign
a project tree in STEP 7 to the real CPU. The top CPU of the two in the tree is always the CPU
with the redundancy ID "1". The bottom CPU has the redundancy ID "2".
If a CPU has a valid hardware configuration and you change the redundancy ID of that CPU,
you also change the CPU's name and IP addresses. You can find more information in the
section Redundancy IDs (Page 252).
3. Assigning system IP addresses
In addition to the device IP addresses of the CPUs, you can also assign system IP addresses for
the S7‑1500R/H redundant system.
You use the system IP addresses for communication with other devices (for example, HMI
devices, CPUs, PG/PC). The devices always communicate over the system IP address with the
primary CPU of the redundant system. This ensures, for example, that the communication
partner can communicate with the new primary CPU (previously backup CPU) in the RUN-Solo
system state after failure of the original primary CPU in redundant operation.
Proceed as follows to activate the system IP address for PROFINET interfaces X1 of the two
CPUs:
1. Select a CPU in the network view. Select the "Properties" tab in the Inspector window.
2. Select the area "PROFINET interface [X1]" and the section "System IP address for switched
communication" in the area navigation.
3. Make sure that the checkbox "Enable the system IP address for switched communication"
is selected for the interface X1. Apply or assign the system IP address in the "IP address"
field.
The subnet mask cannot be modified and corresponds to the subnet mask of the device IP
address.
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S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD