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.

• ✓

  Set the spanning-tree mode to Rapid PVST+

  Why this is correct

  This command globally enables the Rapid PVST+ protocol, which provides faster convergence (around 1-2 seconds) by using explicit proposal/agreement handshakes instead of the classic 802.1D's 50-second timer-based convergence. It is the foundational configuration for this scenario because without it, the switch would run legacy PVST+ or MSTP and would not support the rapid transition capabilities that PortFast and BPDU Guard complement.

• ✓

  Configure the switch as the root bridge for VLAN 1

  Why this is correct

  Because the access ports are on VLAN 1, this switch must be the spanning-tree root for that VLAN to avoid having a blocked alternate port that could cause traffic to traverse unnecessary links or wait for convergence. Setting the priority to a value like 0 or 4096 using the spanning-tree vlan 1 root primary command ensures deterministic path selection and eliminates the risk of a suboptimal root being elected elsewhere.

• ✓

  Enter interface configuration mode for the access ports

  Why this is correct

  PortFast and BPDU Guard are interface-level features, so the engineer must first select the specific switchports (e.g., interface range gi0/1-24) to apply them consistently. Without entering interface configuration mode, these protections cannot be bound to the access ports that connect to hosts, and the configuration would remain global-only, which would not produce the desired per-port behavior.

• ✓

  Enable PortFast on the interfaces

  Why this is correct

  PortFast instantly transitions an access port from blocking to forwarding state, bypassing the Listening and Learning states entirely, which is critical for hosts to obtain DHCP/ARP quickly. This is safe only on ports that connect to end-devices, where no BPDUs are expected; otherwise, it could create a loop if a switch were inadvertently connected.

• ✓

  Enable BPDU Guard on the interfaces

  Why this is correct

  BPDU Guard complements PortFast by placing the interface into an err-disabled state if a BPDU is ever received, which would indicate that someone connected another switch or a misconfigured device to an access port. This real-time safeguard prevents accidental loops and needs to be enabled on the same interface-level commands, typically via spanning-tree bpduguard enable.

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