Cisco WS-C2960S-48LPD-L Software Guide - Page 361
Enabling BPDU Guard, spanning-tree bpduguard enable
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Chapter 17 Configuring Optional Spanning-Tree Features Configuring Optional Spanning-Tree Features Note You can use the spanning-tree portfast default global configuration command to globally enable the Port Fast feature on all nontrunking ports. To disable the Port Fast feature, use the spanning-tree portfast disable interface configuration command. Enabling BPDU Guard When you globally enable BPDU guard on ports that are Port Fast-enabled (the ports are in a Port Fast-operational state), spanning tree shuts down Port Fast-enabled ports that receive BPDUs. In a valid configuration, Port Fast-enabled ports do not receive BPDUs. Receiving a BPDU on a Port Fast-enabled port means an invalid configuration, such as the connection of an unauthorized device, and the BPDU guard feature puts the port in the error-disabled state. When this happens, the switch shuts down the entire port on which the violation occurred. To prevent the port from shutting down, you can use the errdisable detect cause bpduguard shutdown vlan global configuration command to shut down just the offending VLAN on the port where the violation occurred. The BPDU guard feature provides a secure response to invalid configurations because you must manually put the port back in service. Use the BPDU guard feature in a service-provider network to prevent an access port from participating in the spanning tree. Caution Configure Port Fast only on ports that connect to end stations; otherwise, an accidental topology loop could cause a data packet loop and disrupt switch and network operation. You also can use the spanning-tree bpduguard enable interface configuration command to enable BPDU guard on any port without also enabling the Port Fast feature. When the port receives a BPDU, it is put it in the error-disabled state. You can enable the BPDU guard feature if your switch is running PVST+, rapid PVST+, or MSTP. Beginning in privileged EXEC mode, follow these steps to globally enable the BPDU guard feature. This procedure is optional. Step 1 Step 2 Command configure terminal spanning-tree portfast bpduguard default Step 3 interface interface-id Step 4 Step 5 Step 6 Step 7 spanning-tree portfast end show running-config copy running-config startup-config Purpose Enter global configuration mode. Globally enable BPDU guard. By default, BPDU guard is disabled. Specify the interface connected to an end station, and enter interface configuration mode. Enable the Port Fast feature. Return to privileged EXEC mode. Verify your entries. (Optional) Save your entries in the configuration file. OL-8603-04 Catalyst 2960 Switch Software Configuration Guide 17-11
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