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
5.4 Media redundancy (ring topologies)
In order to increase the network availability of an Industrial Ethernet network with optical or
electrical linear bus topologies, you can convert a linear bus topology to a ring topology by
joining the ends together.
Media redundancy in ring topologies
Devices in a ring topology can be IO devices, IO controllers, external switches and/or the
integrated switches of communication modules.
To set up a ring topology with media redundancy, you need to bring together the two free
ends of a linear bus topology in one device. Closing the linear bus topology to form a ring is
achieved with two ports (ring ports) of a device in the ring. One device of the resulting ring
then takes over the role of the redundancy manager. All other devices in the ring are
redundancy clients.
① Redundancy manager
② Test frames
③ Redundancy clients
Figure 5-36 Media redundancy in ring topology
The ring ports of a device are the ports that establish the connection to the two neighboring
devices in the ring topology. The ring ports are selected and set in the configuration of the
relevant device (is also preset, if applicable).