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Entry type: FAQ Entry ID: 109759619, Entry date: 09/04/2018
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What should you watch out for when configuring the PROFINET MRP ring with regard to RSTP packages (Rapid Spanning Tree Protocol)?

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According to the currently valid PROFINET standard there might be unintentional failure of an MRP ring if RSTP packages are in the MRP ring at the same time. This entry describes what is to be done for error-free function when PROFINET segments are connected with other RSTP-compatible network segments in an MRP ring topology.

As an established field bus communication technology, PROFINET offers many advantages and mechanisms like increased data throughput, enhanced plant availability, and integrity in other data networks. One of the classic ways of enhancing the availability of a PROFINET network segment is to use an MRP ring topology that can compensate the failure of an individual device without impairing the network.

According to the currently valid PROFINET standard there might be unintentional failure of an MRP ring if RSTP packages are in the MRP ring at the same time.

The following triggers for negatively influencing an MRP ring have been identified:

  1. Return of a disconnected line connection between two neighboring affected PROFINET devices in the ring (Figure 1)




    Figure 1


  2. Return or start of an affected PROFINET device whose neighbors are also affected PROFINET devices. This can be the result of a restart, a firmware update, switching off and on or a fault on the affected device (Figure 2)



    Figure 2

A detailed list of the affected devices and their firmware versions is available in the additional information in the following document. Furthermore, it is also explained how to ensure error-free function when PROFINET segments are connected with other RSTP-compatible network segments in an MRP ring topology.

 PROFINET - MRP Ring: Important Configuration Recommendations When Using RSTP

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