C
HAPTER
32
| Spanning Tree Commands
– 811 –
COMMAND USAGE
◆ 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.
EXAMPLE
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree loopback-detection
spanning-tree
loopback-detection
action
This command configures the response for loopback detection to block user
traffic or shut down the interface. Use the no form to restore the default.
SYNTAX
spanning-tree loopback-detection action shutdown duration
no spanning-tree loopback-detection action
shutdown - Shuts down the interface.
duration - The duration to shut down the interface.
(Range: 30-86400 seconds)
DEFAULT SETTING
block
COMMAND MODE
Interface Configuration (Ethernet, Port Channel)
COMMAND USAGE
◆ If an interface is shut down by this command, and the release mode is
set to “auto” with the spanning-tree loopback-detection release-mode
command, the 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)#
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