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Siemens Industrial Ethernet Switches SCALANCE X-200 User Manual

Page 24

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Network topologies / media redundancy

2.3 Media redundancy in ring topologies

SCALANCE X-200

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Operating Instructions, 12/2011, A5E00349864-19

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.
The time between the ring interruption and restoration of a functional linear topology is

known as the reconfiguration time.
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.
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 for ring

topologies:
● HSR (High Speed Redundancy)

Reconfiguration time: 0.3 seconds

● MRP (Media Redundancy Protocol)

Reconfiguration time: 0.2 seconds
Automatic configuration of the ring

The mechanisms of these methods are similar. With both methods, up to 50 devices can

participate in the ring. HSR and MRP cannot be used in the ring at the same time.
If you configure your plant using STEP 7, you can only select MRP as the media redundancy

method.
If you configure your devices with Web Based Management, CLI or SNMP, you can choose

either HSR or MRP.

Media redundancy with IRT

For ring topologies in which MRP is activated, the "MRPD" function is activated automatically

for IRT devices capable of IRT, if this is supported by the device.
● MRPD (Media Redundancy with Path Duplication)

For use only with SCALANCE X-200IRT
This procedure allows redundancy with IRT. You will find details in the section MRPD

(Page 27).