Xerox KS-801 - Manual (Page 49)

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Advanced / Spanning
Spanning-Tree Protocol is a link management protocol that provides
path redundancy while preventing undesirable loops in the network. For
an Ethernet network to function properly, only one active path must exist
between two stations.
Multiple active paths between stations cause loops in the network. If a
loop exists in the network, you might receive duplicate messages. When
loops occur, some switches see stations on both sides of the switch.
This condition confuses the forwarding algorithm and allows duplicate
frames to be forwarded.
To provide path redundancy, Spanning-Tree Protocol defines a tree that
spans all switches in an extended network. Spanning-Tree Protocol forces
certain redundant data paths into a standby (blocked) state. If one net-
work segment in the Spanning-Tree Protocol becomes unreachable, or if
Spanning-Tree Protocol costs change, the spanning-tree algorithm
reconfigures the spanning-tree topology and reestablishes the link by
activating the standby path.
Spanning-Tree Protocol operation is transparent to end stations, which
are unaware whether they are connected to a single LAN segment or a
switched LAN of multiple segments.