Siemens SCALANCE X-200 Configuration Manual page 17

To increase availability, optical or electrical bus topologies made up of X-200 IE switches
with a redundancy manager can be closed to form a ring. The following IE switches can be
configured as the redundancy manager:
● SCALANCE X-200
● SCALANCE X-300
● SCALANCE X-400
● OSM / ESM version 2
The X-200 IE switches are first connected over their ring ports to form a bus. The two ends
of the line are closed to form a ring by the switch operating as redundancy manager.
When a switch is used as the redundancy manager, the ring ports are isolated from each
other if the network is operating problem-free.
The IE switch operating as redundancy manager monitors the connected bus via its ring
ports. If the connected bus is interrupted, it switches the ring ports through; in other words, it
re-establishes a functioning bus via this alternative path. Reconfiguration takes place within
0.3 seconds.
As soon as the problem has been eliminated, the original topology is restored; in other
words, the ring ports in the redundancy manager are once again disconnected from each
other.
SCALANCE X-200
Configuration Manual, 03/2015, C79000-G8976-C285-06
Network topologies and media redundancy
1.1 Network topologies
17