Siemens SIMATIC PCS 7 System Manual page 70

I/O configuration variants
4.6 System and media redundancy at the PROFINET IO interface
You can enable the media redundancy protocol (MRP) for IO devices, switches, and CPUs
with PROFINET IO interface V8.0 or higher in STEP 7 -> HW Config. MRP is a component
of the PROFINET IO standardization according to IEC 61158.
In media redundancy with MRP, one device is the media redundancy manager (MRM), and
all other devices are redundancy clients.
Installing a ring topology
To set up a ring topology with media redundancy, you must join both free ends of a line
network topology in the same device. You join the line topology to form a ring via two ports
(ring ports, port ID "R") of a device connected to the ring.
The data paths between the individual devices are automatically reconfigured if the ring is
interrupted at any point. The devices are available again after reconfiguration.
Topology
You can also combine media redundancy under PROFINET IO with other PROFINET IO
functions.
Media redundancy
Figure 4-15
70
Configuration example of media redundancy
CPU 410-5H Process Automation/CPU 410 SMART
System Manual, 09/2014, A5E32631667-AB