Cisco WS-C2960S-24PD-L Software Guide - Page 175

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: Step 1 Step 2 Command configure terminal spanning-tree portfast bpduguard Step 3 Step 4 Step 5 end show spanning-tree summary total copy running-config startup-config Purpose Enter global configuration mode. Enable BPDU guard on the switch. By default, BPDU guard is disabled on the switch. Return to privileged EXEC mode. Verify your entries. (Optional) Save your entries in the configuration file. Use the no spanning-tree portfast bpduguard global configuration command to disable BPDU guard. 78-6511-08 Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide 6-47