Siemens SIMATIC ET 200AL, System Manual

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Functions
5.4 Media redundancy (ring topologies)
PROFINET with STEP 7
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Function Manual, 05/2021, A5E03444486-AL
In the example, Switch 1 belongs to two MRP rings. Ring 1 is formed by Switch 1 and PLC 1,
Ring 2 by Switch 1 and IO device 1.
STEP 7 automatically assigns the "Manager" role to the switch. The other devices receive the
"Client" role.
The manager is located at the point of intersection of the two rings 1 and 2. The manager
monitors the two rings separately. To do this, it uses two MRP instances.
One MRP instance checks whether all devices in ring 1 are reachable, another instance
monitors whether all devices in ring 2 are reachable (only one device in each case in the
example).
You can configure each MRP instance separately.
The following figure shows the two MRP instances in the manager (PROFINET interface of the
switch). Here in the example, MRP instance 1 checks whether the devices in the MRP domain
"mrpdomain-1" can be reached. The MRP instance 2 is responsible for monitoring the devices
of the MRP domain "mrpdomain-2".
Figure 5-44 Setting media redundancy for multiple rings