Chapter 19
| Spanning Tree Commands
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Default Setting
auto
Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
â—† 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:
â–
The port receives any other BPDU except for it’s own, or;
â–
The port’s link status changes to link down and then link up again, or;
â–
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).
â—† Port Loopback Detection will not be active if Spanning Tree is disabled on the
switch.
â—† 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)
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