C
HAPTER
33
| Spanning Tree Commands
– 1075 –
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.
◆ When configured for manual release mode, then a link down / up event
will not release the port from the discarding state. It can only be
released using the spanning-tree loopback-detection release command.
EXAMPLE
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree loopback-detection release-mode manual
Console(config-if)#
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