Siemens SIMATIC PCS 7 Function Manual page 122

Advantages of fault-tolerant components
4.3 Communication connections
3. Select the "Graphic View" tab.
Note:
You can move the displayed objects. You can select the section displayed via the thumbnail
view. Position the objects in accordance with the cable sequence in the system.
4. Using drag-and-drop, connect the I/Os of the PROFINET-capable modules (CPU or CP)
and the interface modules (green squares) in accordance with the cable sequence in the
system. Connection path for an interface of the PROFINET-capable module:
From Port1 > via the interface modules of the distributed I/O > to Port 2
You can make additional system-specific settings on the "Table View" tab. For additional
information, refer to the online help of the dialog box.
Configuring media redundancy (interface PN IO...)
Note
Media redundancy
Only one MRP ring can be operated on a PROFINET interface.
If you are operating multiple MRP rings on a CPU with multiple PROFINET interfaces, you
must not connect the MRP rings to one another.
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Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA