Siemens SCALANCE X-300 Series Operating Instructions Manual page 28

Network topologies
3.5 Redundant coupling of network segments
IE Switches X-300 connected in the configuration exchange data frames with each other to
synchronize their operating statuses (one device is master and the other slave). If there are no
problems, only the link from the master to the other network segment is active. If this link fails
(for example due to a link-down or a device failure), the slave activates its link as long as the
problem persists. Reconfiguration takes place within 0.3 s.
Note
If IE Switches X-300 or SCALANCE X408-2 devices are used exclusively for redundant
coupling of the gigabit rings, the coupling links can also be designed with a gigabit transmission
rate.
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Operating Instructions, 11/2019, A5E01113043-24
SCALANCE X-300