Hirschmann RS20 Reference Manual page 176

Redundancy
Parameters Meaning
Loop Guard The "Loop Guard" setting is only meaningful
for ports with the STP role alternate,
backup or root. If the "Loop Guard" setting is
active and the port has not received any STP-
BPDUs for a while, the device sets the port to
the discarding condition (port sends no
more data).
The device also sets the port to what is known
as the "loop inconsistent status" and displays
this in the "Loop Status" column.
The device prevents a potential loop if no more
STP-BPDUs are received if, for example, you
switch STP off on the remote device, or the link
only fails in the receiving direction.
When the port receives BPDUs again, the
device resets the loop status of the port to
false, and the transmission status of the port
according to the port role.
If the "Loop Guard" setting is inactive,
however, the device sets the port to the
forwarding status when STP-BPDUs have
not been received.
Note: The "Root Guard" and "Loop Guard"
settings are mutually exclusive. If you activate
one setting when the other is already active,
the device switches off the other one.
Loop State (read Display the status of the Loop Status.
only) The device sets the loop status of the port to
true if the "Loop Guard" setting is active at
the port and the port is not receiving any more
STP-BPDUs.
Here the device leaves the port in the
discarding transmission status, thus
helping to prevent a potential loop.
When the port receives STP-BPDUs again,
the device resets the loop status to false.
Transitions to Counts how often the device has set the port
Loop Status to the loop status ("Loop Status" column
(read only)
true).
Table 111:Port-related STP settings and displays, guards
176
6.3 Spanning Tree
Possible values Default
setting
active (box
inactiv
selected),
e
inactive (box
empty)
-
true, false
0 - 4294967295 0
32
(2 -1)
RM GUI L2E
Release 8.0 05/2013