Understanding and Configuring Loop Protect
15-34 Configuring Spanning Tree
Enabling or Disabling Loop Protect
By default, Loop Protect is disabled on all ports. Use this command to enable (or, if desired,
disable) the feature on one or more ports:
set spantree lp port-string {enable | disable} [sid sid]
If no SID is specified, SID 0 is assumed.
This command takes precedence over per port STP enable/disable state (portAdmin). Normally,
portAdmin disabled would cause a port to go immediately to forwarding. If Loop Protect is
enabled, that port should go to listening and remain there.
Specifying Loop Protect Partners
By default, each port is not set as a Loop Protect capable partner. If the port is set as a Loop Protect
capable partner (true), the full functionality of the Loop Protect feature is used. If the value is false,
then there is some ambiguity as to whether an Active Partner timeout is due to a loop protection
event or is a normal situation due to the fact that the partner port does not transmit Alternate
Agreement BPDUs. Therefore, a conservative approach is taken in that designated ports will not
be allowed to forward unless receiving agreements from a port with root role. This type of timeout
will not be considered a loop protection event. Loop protection is maintained by keeping the port
from forwarding, but since this is not considered a loop event, it will not be factored into locking
the port.
Use this command to set the Loop Protect partner state on one or more ports:
set spantree lpcapablepartner port-string {true | false}
Setting the Loop Protect Event Threshold and Window
The Loop Protect event threshold is a global integer variable that provides protection in the case of
intermittent failures. The default value is 3. If the event counter reaches the threshold within a
given period (the event window), the port for the given SID becomes locked (that is, held
indefinitely in the blocking state). If the threshold is 0, the ports are never locked.
Use this command to set the Loop Protect event threshold:
set spantree lpthreshold value
The Loop Protect window is a timer value, in seconds, that defines a period during which Loop
Protect events are counted. The default value is 180 seconds. If the timer is set to 0, the event
counter is not reset until the Loop Protect event threshold is reached.
Use this command to set the Loop Protect event window value in seconds:
set spantree lpwindow value
Setting the Loop Protect Event Threshold and Window 15-34
Enabling or Disabling Loop Protect Event Notifications 15-35
Setting the Disputed BPDU Threshold 15-35
Monitoring Loop Protect Status and Settings 15-35
For information about... Refer to page...
Note: The Loop Protect enable/disable settings for an MSTI port should match those for the CIST
port.
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