Siemens S7-300 Configuration Manual page 71

The two ring ports of a device are the ports that establish the connection to its two
neighboring devices in the ring topology. The ring ports are selected and set in the
configuration of the relevant device. In STEP 7 and on the S7 Ethernet CP modules
themselves, the ring ports are indicated by an "R" after the port number.
Note
Before physically closing the ring, download the configuration of your STEP 7 project to the
individual devices.
How media redundancy works in a ring topology
When using media redundancy, the data paths between the individual devices are
reconfigured if the ring is interrupted at one point. Following reconfiguration of the topology,
the devices can once again be reached in the resulting new topology.
In the redundancy manager, the 2 ring ports are disconnected from each other if the network
is uninterrupted. This prevents circulating data frames. In terms of data transmission, the ring
topology is a linear bus topology. The redundancy manager monitors the ring topology. It
does this by sending test frames both from ring port 1 and ring port 2. The test frames run
round the ring in both directions until they arrive at the other ring port of the redundancy
manager.
An interruption of the ring can be caused by loss of the connection between two devices or
by failure of a device in the ring.
If the test frames of the redundancy manager no longer arrive at the other ring port, the
redundancy manager connects its two ring ports. This substitute path once again restores a
functioning connection between all remaining devices in the form of a linear bus topology.
As soon as the interruption is eliminated, the original transmission paths are established
again, the two ring ports of the redundancy manager are disconnected and the redundancy
clients informed of the change. The redundancy clients then use the new paths to the other
devices.
The time between the ring interruption and restoration of a functional linear topology is
known as the reconfiguration time.
If the redundancy manager fails, the ring becomes a functional linear bus.
Media redundancy methods
The following media redundancy methods are supported by SIMATIC NET products:
● HRP (High Speed Redundancy Protocol)
● MRP (Media Redundancy Protocol)
The mechanisms of these methods are similar. HRP and MRP cannot be used in the ring at
the same time.
Configuring and commissioning S7 CPs for Industrial Ethernet
Configuration Manual, 09/2013, C79000-G8976-C182-13
Reconfiguration time: 0.3 seconds
Reconfiguration time: 0.2 seconds
Configuring the Ethernet CP with STEP 7
3.5 Media redundancy
71