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Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
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Chapter 6 Configuring the System
Configuring STP
Configuring BPDU Guard
Note
This feature is not available on the Catalyst 2900 LRE XL switches.
In a valid configuration, Port Fast-enabled interfaces do not receive BPDUs. When the BPDU guard
feature is enabled on the switch, STP shuts down Port Fast-enabled interfaces that receive BPDUs rather
than putting the interfaces into the blocking state.
Note
When enabled on the switch, STP applies the BPDU guard feature to all Port Fast-enabled interfaces.
Caution
The BPDU guard feature works on Port Fast-enabled interfaces. Configure Port Fast only on interfaces
that connect to end stations; otherwise, an accidental topology loop could cause a data packet loop and
disrupt switch and network operation.
Beginning in privileged EXEC mode, follow these steps to enable the BPDU guard feature on the switch:
Use the no spanning-tree portfast bpduguard global configuration command to disable BPDU guard.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree portfast bpduguard
Enable BPDU guard on the switch.
By default, BPDU guard is disabled on the switch.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree summary total
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.