Enabling Backbonefast; Enabling Root Guard - Cisco Catalyst 3750 Software Configuration Manual

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+. It is not supported when
the switch is running rapid PVST+ or MSTP.
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 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.
You cannot enable both root guard and loop guard at the same time.
Note
You can enable this feature if your switch is running PVST+, rapid PVST+, or MSTP.
Beginning in privileged EXEC mode, follow these steps to enable root guard on an interface. This
procedure is optional.
Command
Step 1 configure terminal
Step 2 interface interface-id
Step 3
spanning-tree guard root
Catalyst 3750 Metro Switch Software Configuration Guide
16-14
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.
Specify an interface to configure, and enter interface configuration mode.
Enable root guard on the interface.
By default, root guard is disabled on all interfaces.
Chapter 16 Configuring Optional Spanning-Tree Features
78-15870-01