Siemens SIMATIC PCS 7 CPU 410-5H System Manual page 258

Supplementary information
15.7 Basics and terminology of fault-tolerant communication
The following examples and the possible configurations in STEP 7 are based on a maximum
of two subnets and a maximum of 4 CPs in the redundant fault-tolerant system.
Configurations with a higher number of CPs or networks are not supported in STEP 7.
Figure 15-7
258
Example that shows that the number of resulting partial connections depends on the
configuration
CPU 410-5H Process Automation
System Manual, 09/2014, A5E31622160-AB