CompTIA Network+ (N10-009)Network ImplementationMedium
A network administrator wants to protect the spanning tree topology by ensuring that if any BPDU is received on a designated access port connected to end-user devices, the port is immediately disabled rather than allowed to participate in STP calculations. Which feature should be configured on that port?
- ABPDU Guard
- BRoot Guard
- CUplinkFast
- DLoop Guard
Show answer & explanationAnswer & explanation
Correct answer: A. BPDU Guard
BPDU Guard is applied to access ports (typically along with PortFast) to immediately err-disable the port if any BPDU is received, preventing rogue switches from participating in the spanning tree topology. Root Guard, by contrast, only blocks a port from becoming the root port if it receives a superior BPDU, but doesn't disable the port on every BPDU.
Why the other options are wrong
- B. Root Guard prevents a port from becoming root but only reacts to superior BPDUs, not any BPDU.
- C. UplinkFast speeds up convergence after a link failure on access switches, not BPDU filtering.
- D. Loop Guard prevents unidirectional link failures from causing loops, unrelated to BPDU reception on access ports.
BPDU Guard
An STP feature applied to access ports that immediately err-disables the port if a BPDU is received, protecting the network from rogue switches or accidental loops.
- Typically paired with PortFast on edge ports
- Disables port entirely, unlike Root Guard which just blocks root role
- Requires manual or automatic recovery to re-enable port
Memory trick: BPDU Guard slams the door the instant it hears any BPDU knock.