Which statement correctly describes enabling BPDU guard on an access port that is also
enabled for PortFast?
A.
Upon startup, the port transmits 10 BPDUs. If the port receives a BPDU, PortFast and
BPDU guard are disabled on that port and it assumes normal STP operation.
B.
The access port ignores any received BPDU.
C.
If the port receives a BPDU, it is placed into the error-disable state.
D.
BPDU guard is configured only globally and the BPDU filter is required for port-level
configuration.
Explanation:
When enabled on a port, BPDU Guard shuts down a port that receives a BPDU. When
configured globally, BPDU Guard is only effective on ports in the operational PortFast state.
In a valid configuration, PortFast Layer 2 LAN interfaces do not receive BPDUs. Reception
of a BPDU by a PortFast Layer 2 LAN 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 Layer 2 LAN interface back
in service. With release 12.1(11b)E, BPDU Guard can also be configured at the interface
level. When configured at the interface level, BPDU Guard shuts the port down as soon as
the port receives a BPDU, regardless of the PortFast configuration.
Reference:
http://www.cisco.com/en/US/docs/routers/7600/ios/12.1E/configuration/guide/stp_enha.html#wp1020395