CCNA Practice Exam Test Sample – Question 241

Which Cisco Catalyst feature automatically disables the port in an operational PortFast upon receipt of a BPDU?

A. BackboneFast
B. UplinkFast
C. Root Guard
D. BPDU Guard
E. BPDU Filter

Correct Answer: D
Section: Network Device Security

Explanation:
We only enable PortFast feature on access ports (ports connected to end stations). But if someone does not know he can accidentally plug that port to another switch and a loop may occur when BPDUs are being transmitted and received on these ports.
With BPDU Guard, when a PortFast receives a BPDU, it will be shut down to prevent a loop.