CCNA Switching and Network Access Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  PortFast on user-facing access ports

  Why this is correct

  PortFast is a spanning-tree feature that immediately transitions a switch port from blocking to forwarding when the link comes up, bypassing the 15-second listening and 15-second learning states required by legacy 802.1D. For user-facing access ports, this eliminates the forwarding delay, allowing an end host to obtain a DHCP lease and start communicating almost instantly. It is the primary mechanism for rapid transition to forwarding on edge endpoints.

• ✓

  BPDU Guard on those same access ports

  Why this is correct

  BPDU Guard is a protective feature that immediately error-disables a PortFast edge port if any BPDU is received, preventing an unauthorized switch from creating a loop. It is correct to enable BPDU Guard on the same user-facing access ports as PortFast because it secures the fast-forwarding port without delaying host traffic. Although BPDU Guard does not itself shorten the forwarding transition, it ensures that the PortFast-enabled port remains an endpoint and does not cause instability.

• ✗

  Root Guard on every user-facing port instead of PortFast

  Why it's wrong here

  Root Guard forces a port to remain a designated port and blocks the port from becoming a root port, preserving the intended spanning-tree root location. It does not alter the normal listening and learning timers, so an end-user workstation would still experience the standard 30-second delay before traffic can be forwarded. Using Root Guard instead of PortFast on every user-facing port would therefore fail to achieve rapid transition to forwarding; it is designed for switch-to-switch topology protection, not edge access.

  When this WOULD be correct

  Root Guard would be correct in a question asking: 'Which STP feature prevents an unauthorized switch from becoming the root bridge on a specific port?'

• ✗

  Loop Guard on hosts to accelerate DHCP

  Why it's wrong here

  Loop Guard is a spanning-tree protocol feature that detects unidirectional link failures by monitoring BPDU reception and placing a non-designated port into loop-inconsistent state when BPDUs stop arriving. It is configured on switch ports that participate in spanning tree, never on end hosts, and it has no relationship to DHCP or host startup timing. Consequently, applying Loop Guard to hosts would be both invalid and useless for accelerating DHCP, because it neither forwards traffic faster nor addresses client configuration.

  When this WOULD be correct

  In a question asking for a feature that prevents bridging loops caused by unidirectional link failures on point-to-point links, Loop Guard would be the correct answer.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

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