Chapter 18
| Spanning Tree Commands
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selected interface will be automatically enabled when the shutdown interval
has expired.
◆ If an interface is shut down by this command, and the release mode is set to
“manual,” the interface can be re-enabled using the spanning-tree loopback-
detection release command.
Example
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree loopback-detection action shutdown 600
Console(config-if)#
spanning-tree
loopback-detection
release-mode
This command configures the release mode for a port that was placed in the
discarding state because a loopback BPDU was received. Use the no form to restore
the default.
Syntax
spanning-tree loopback-detection release-mode {auto | manual}
no spanning-tree loopback-detection release-mode
auto - Allows a port to automatically be released from the discarding state
when the loopback state ends.
manual - The port can only be released from the discarding state manually.
Default Setting
auto
Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
◆ If the port is configured for automatic loopback release, then the port will only
be returned to the forwarding state if one of the following conditions is
satisfied:
■
The port receives any other BPDU except for it’s own, or;
■
The port’s link status changes to link down and then link up again, or;
■
The port ceases to receive it’s own BPDUs in a forward delay interval.
◆ If Port Loopback Detection is not enabled and a port receives it’s own BPDU,
then the port will drop the loopback BPDU according to IEEE Standard 802.1W-
2001 9.3.4 (Note 1).
◆ Port Loopback Detection will not be active if Spanning Tree is disabled on the
switch.
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