Cisco Systems 4500 About BPDU Guard

21-8
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 21 Configuring Optional STP Features
About BPDU Guard
This example shows how to enable PortFast on Fast Ethernet interface 5/8:
Switch(config)# interface fastethernet 5/8
Switch(config-if)# spanning-tree portfast
Switch(config-if)# end
Switch#
This example shows how to verify the configuration:
Switch# show running-config interface fastethernet 5/8
Building configuration...
Current configuration:
!
interface FastEthernet5/8
no ip address
switchport
switchport access vlan 200
switchport mode access
spanning-tree portfast
end
Switch#
About BPDU Guard
Spanning Tree BPDU guard shuts down PortFast-configured interfaces that receive BPDUs, rather than
putting them into the spanning tree blocking state. In a valid configuration, PortFast-configured
interfaces do not receive BPDUs. Reception of a BPDU by a PortFast-configured interface signals an
invalid configuration, such as connection of an unauthorized device. BPDU guard provides a secure
response to invalid configurations, because the administrator must manually put the interface back in
service.
Note When the BPDU guard feature is enabled, spanning tree applies the BPDU guard feature to all
PortFast-configured interfaces.
Note To prevent the port from shutting down, use the errdisable detect cause bpduguard shutdown
vlan global configuration command to shut down only the offending VLAN on the port where
the violation occurred.
Step 3 Switch(config-if)# end Exits configuration mode.
Step 4 Switch# show running interface {{fastethernet |
gigabitethernet | tengigabitethernet} slot/port}
| {port-channel port_channel_number}
Verifies the configuration.
Command Purpose