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Catalyst 2940 Switch Software Configuration Guide
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Chapter 12 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
To disable the BackboneFast feature, use the no spanning-tree backbonefast global configuration
command.
Enabling EtherChannel Guard (Optional)
You can enable EtherChannel guard to detect an EtherChannel misconfiguration that causes a loop.
Beginning in privileged EXEC mode, follow these steps to enable EtherChannel guard. This procedure
is optional:
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 determine 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 commands on the
port-channel interfaces that were misconfigured.
Enabling Root Guard (Optional)
Root guard enabled on an interface applies to all the VLANs to which the interface belongs.
Do not enable the root guard on interfaces to be used by the UplinkFast feature. With UplinkFast, the
backup interfaces (in the blocked state) replace the root port in the case of a failure. However, if root
guard is also enabled, all the backup interfaces used by the UplinkFast feature are placed in the
root-inconsistent state (blocked) and are prevented from reaching the forwarding state.
Note You cannot enable both root guard and loop guard at the same time.
Beginning in privileged EXEC mode, follow these steps to enable root guard on an interface. This
procedure is optional:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree etherchannel guard
misconfig
Enable EtherChannel guard.
Step 3
end Return to privileged EXEC mode.
Step 4
show spanning-tree summary Verify your entries.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify an interface to configure.