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Configuring Optional Spanning-Tree Features
You can configure the BackboneFast feature for rapid PVST+ or for the MSTP, but the feature remains
disabled (inactive) until you change the spanning-tree mode to PVST+.
Beginning in privileged EXEC mode, follow these steps to enable BackboneFast. This procedure is
optional.
Command
Step 1
configure terminal
Step 2
spanning-tree backbonefast
Step 3
end
Step 4
show spanning-tree summary
Step 5
copy running-config startup-config
To disable the BackboneFast feature, use the no spanning-tree backbonefast global configuration
command.
Enabling EtherChannel Guard
You can enable EtherChannel guard to detect an EtherChannel misconfiguration if your switch is
running PVST+, rapid PVST+, or MSTP.
Beginning in privileged EXEC mode, follow these steps to enable EtherChannel guard. This procedure
is optional.
Command
Step 1
configure terminal
Step 2
spanning-tree etherchannel guard
misconfig
Step 3
end
Step 4
show spanning-tree summary
Step 5
copy running-config startup-config
To disable the EtherChannel guard feature, use the no spanning-tree etherchannel guard misconfig
global configuration command.
You can use the show interfaces status err-disabled privileged EXEC command to show which switch
ports are disabled because of an EtherChannel misconfiguration. On the remote device, you can enter
the show etherchannel summary privileged EXEC command to verify the EtherChannel configuration.
After the configuration is corrected, enter the shutdown and no shutdown interface configuration
commands on the port-channel interfaces that were misconfigured.
Catalyst 2928 Switch Software Configuration Guide
18-14
Chapter 18
Configuring Optional Spanning-Tree Features
Purpose
Enter global configuration mode.
Enable BackboneFast.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Purpose
Enter global configuration mode.
Enable EtherChannel guard.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
OL-23389-01
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Troubleshooting
