You are the administrator of a switch and currently all host-connected ports are configured
with the portfast command. You have received a new directive from your manager that
states that, in the future, any host-connected port that receives a BPDU should automatically
disable PortFast and begin transmitting BPDUs. Which command will support this new
requirement?

A.
Switch(config)#spanning-tree portfast bpduguard default

B.
Switch(config-if)#spanning-tree bpduguard enable

C.
Switch(config-if)#spanning-tree bpdufilter enable

D.
Switch(config)#spanning-tree portfast bpdufilter default

Explanation:
When spanning-tree bpdufilter enable either on interface configuration or on global
configuration mode prevents from sending or receiving Bridge Protocol Data Units on
portfast enabled interface.
To enable bpdufilter global configuration mode:
Device1(Config)#spanning-tree portfast bpdufilter default
Be careful when enabling BPDU filtering. Functionality is different when enabling on a perport basis or globally. When enabled globally, BPDU filtering is applied only on ports that are
in an operational PortFast state. Ports still send a few BPDUs at linkup before they
effectively filter outbound BPDUs. If a BPDU is received on an edge port, it immediately
loses its operational PortFast status and BPDU filtering is disabled.
Reference:
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.1E/native/command/reference/S1.html#wp1180453