350-401 · Question #233
350-401 Question #233: Real Exam Question with Answer & Explanation
The correct answer is B: It minimizes spanning-tree convergence time. Spanning-Tree PortFast Explained PortFast bypasses the normal STP listening and learning states (which can take 30–50 seconds) and allows an access port to transition directly to forwarding, dramatically reducing convergence time for end devices like PCs and servers - making B co
Question
What is the primary effect of the spanning-tree portfast command?
Options
- AIt enables BPDU messages
- BIt minimizes spanning-tree convergence time
- CIt immediately puts the port into the forwarding state when the switch is reloaded
- DIt immediately enables the port in the listening state
Explanation
Spanning-Tree PortFast Explained
PortFast bypasses the normal STP listening and learning states (which can take 30–50 seconds) and allows an access port to transition directly to forwarding, dramatically reducing convergence time for end devices like PCs and servers - making B correct.
Why the distractors are wrong:
- A is incorrect because PortFast does not enable BPDU messages; it actually works alongside BPDU Guard, which blocks unexpected BPDUs on PortFast-enabled ports
- C is partially misleading - while the port does reach forwarding quickly, the key benefit is the overall reduction in convergence time, not just behavior during a reload
- D is incorrect because PortFast skips the listening state entirely, not enables it
💡 Memory Tip: Think of PortFast as a "fast pass" at a theme park - end devices (PCs, printers) skip the long STP queue (listening → learning) and go straight to forwarding. It's designed for access ports connected to end hosts only, never trunk or switch-to-switch links, since a switch connected to a PortFast port could cause bridging loops.
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