C
HAPTER
35
| Spanning Tree Commands
– 823 –
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)#
spanning-tree
loopback-detection
trap
This command enables SNMP trap notification for Spanning Tree loopback
BPDU detections. Use the no form to restore the default.
SYNTAX
[no] spanning-tree loopback-detection trap
DEFAULT SETTING
Disabled
COMMAND MODE
Interface Configuration (Ethernet, Port Channel)
EXAMPLE
Console(config)#interface ethernet ethernet 1/5
Console(config-if)#spanning-tree loopback-detection trap
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