Siemens SIMATIC S7-1500 Function Manual page 330

IP forwarding via the system IP address
If you use the system IP addresses as the gateway/default route for IP routes through the
S7-1500R/H redundant system, IP packets are forwarded even if one CPU fails.
In the following figure, the PC is connected to the two X2 interfaces of the S7-1500R CPUs.
Enter the system IP address X2 as gateway in the PC for the route to the HMI device. The
HMI device is connected to the PROFINET ring of the redundant system S7-1500 via a
switch. The system IP address X1 is configured as router in the HMI device.
Figure 13-4
Communication
Function Manual, 11/2019, A5E03735815-AH
Example: IP forwarding via the system IP address
Communication with the redundant system S7-1500R/H
13.1 System IP addresses
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