Siemens SIMATIC PCS 7 Configuration Manual page 146

Configuration of the network connections
7.2 Configuration of the connections
This connection contains four routes internally from which the first is activated in operation.
The second route is a reserve and it automatically takes on the active role in the event of a
fault. The third and fourth routes are dismantled at the beginning.
Fault-tolerant communication (2-way or 4-way)
A "S7 connection fault-tolerant" is always used for communication between fault-tolerant
systems. The following connection partners are possible:
● For a simple plant bus:
– Standard AS with CPU 41xH, and 1x CP 443-1 if required
– H system with 2x CP 443-1
– PC station with C16xx
● For a redundant plant bus
– Standard AS with CPU 41xH, and 2x CP 443-1 if required
– H system with 2x or 4x CP 443-1
– PC station with 2x CP16xx
146
Compendium Part A - Configuration Guidelines (V8.2)
Configuration Manual, 08/2016, A5E38166869-AA