Functions
5.4 Media redundancy (ring topologies)
PROFINET with STEP 7 V15
Function Manual, 12/2017, A5E03444486-AH
163
Figure 5-34 Example of a ring topology with the MRP media redundancy protocol:
The following rules apply to a ring topology with media redundancy using MRP:
● All devices must be connected to one other via their ring ports.
● All devices in the ring belong to the same redundancy domain.
● A device in the ring takes on the task of a redundancy manager.
– One device only has the role of "Manager". No other device may have the role of
"Manager". Or
– Several devices in the ring have the role of "Manager (auto)". The devices with the
role of "Manager (auto)" then negotiate between themselves which device is to take
on the role of redundancy manager. In this case, no device is permitted to have the
role of "Manager".
● All other devices in the ring are redundancy clients.
● You can connect up to 50 devices in a ring.
Non MRP-compliant devices can, for example, be connected to the ring via a SCALANCE X
switch or via a PC with a CP 1616.
Rules for loading the devices of an MRP domain
When loading devices of an MRP domain, frame loops can occur and result in network
failure if there is an invalid MRP configuration.
Example: You change the MRP roles of several devices and consecutively load the
configuration into the devices involved. Configurations can arise that contradict the roles
mentioned above, for example, there may be devices that simultaneously have the
"Manager" and "Manager (auto)" roles in the ring.
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