The used topology (line, star, ring) plays no role for the system redundancy. This distinguishes the system redundancy from the media redundancy. System redundant periphery is often also referred to as switched I/O. This does not refer to the fault tolerance between I/O groups or systems.

Media redundancy ensures the network availability and contributes to increasing the plant availability. The ring topology is used here. The media redundancy protocol (MRP) ensures

that when one transmission path fails, an alternative communication path is available.

The nodes with PROFINET interface interconnected in the ring use MRP as of V6.0, if MRP-capable. MRP is part of the PROFINET standardization according to IEC 61158. For media redundancy with MRP, one device is the media redundancy manager (MRM), all other devices are redundancy clients.

Hope this helps

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Navnag