Hirschmann RS20 User Manual page 73

Spanning Tree

Edge port
Every network segment with no additional RSTP bridges is connected
with exactly one designated port. In this case, this designated port is also
an edge port. The distinction of an edge port is the fact that it does not
receive any RST BPDUs (Rapid Spanning Tree Bridge Protocol Data
Units).

Alternate port
This is a blocked port that takes over the task of the bridge port if the
connection to the root bridge is lost. The alternate port provides a backup
connection to the root bridge.
 Backup port
This is a blocked port that serves as a backup in case the connection to
the designated port of this network segment (without any RSTP bridges)
is lost
 Disabled port
This is a port that does not participate in the Spanning Tree Operation,
i.e., the port is switched off or does not have any connection.
UM Redundancy Configuration L2E
Release 7.1 12/2011
5.6 The Rapid Spanning Tree
Protocol
73