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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 13 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Enabling BackboneFast
You can enable BackboneFast to detect indirect link failures and to start the spanning-tree
reconfiguration sooner.
Note If you use BackboneFast, you must enable it on all switches in the network. BackboneFast is not
supported on Token Ring VLANs. This feature is supported for use with third-party switches.
The BackboneFast feature is supported only when the switch is running PVST.
Beginning in privileged EXEC mode, follow these steps to enable BackboneFast:
To disable the BackboneFast feature, use the no spanning-tree backbonefast global configuration
command.
Enabling Root Guard
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.
You can enable this feature if your switch is running PVST or MSTP. The MSTP is available only if you
have the EI installed on your switch.
Beginning in privileged EXEC mode, follow these steps to enable root guard on an interface:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree backbonefast Enable BackboneFast.
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.
Step 3
spanning-tree guard root Enable root guard on the interface.
By default, root guard is disabled on all interfaces.
Step 4
end Return to privileged EXEC mode.