Question 1,052 of 1,819
Switching and Network AccesshardConfigurationObjective-mapped

Make a Switch the Root Bridge and Secure Edge Ports with PortFast + BPDU Guard

This 200-301 practice question tests your understanding of switching and network access. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Network Topology
G0/1 to PCSW2SW1SW3

You are connected to SW1 via the console. SW1 is a Layer 2 switch connected to two other switches (SW2 and SW3) via redundant links. All switches run IEEE 802.1D Spanning Tree Protocol. The network administrator wants SW1 to become the root bridge for VLAN 1. Currently, the root bridge is SW2. Configure SW1 to achieve this and ensure that port G0/1, which connects to an end device, immediately transitions to forwarding state upon link up and is protected from BPDU attacks.

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

  • Clue: "immediately / without restart"

    Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.

Quick Answer

The answer is to configure 'spanning-tree vlan 1 root primary' globally, and on interface G0/1 apply 'spanning-tree portfast' and 'spanning-tree bpduguard enable'. This works because the root primary command dynamically sets SW1’s bridge priority to 24576, which is lower than the default 32768, ensuring SW1 becomes the root bridge for VLAN 1 by forcing a new STP election. PortFast on G0/1 immediately transitions the access port to the forwarding state, bypassing the listening and learning phases, while BPDU Guard protects that edge port by error-disabling it if any BPDU is received, preventing rogue switch attacks. On the CCNA 200-301 v2 exam, this tests your ability to combine STP root selection with Layer 2 security features in a single scenario—a common trap is forgetting that PortFast alone does not block BPDUs, so BPDU Guard must be explicitly enabled. A useful memory tip: “Root primary for the king, PortFast for the edge, BPDU Guard for the hedge.”

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

Configure 'spanning-tree vlan 1 root primary' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'.

The 'spanning-tree vlan 1 root primary' command reduces the bridge priority to 24576 (or lower) to ensure SW1 becomes root for VLAN 1. PortFast on G0/1 speeds up access port convergence, and BPDU Guard protects against rogue switches by disabling the port upon BPDU reception.

Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.

Answer analysis

Option-by-option breakdown

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

  • Configure 'spanning-tree vlan 1 root primary' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'.

    Why this is correct

    This is correct because 'spanning-tree vlan 1 root primary' sets the bridge priority to 24576 (or lower if needed) to ensure SW1 becomes root for VLAN 1. PortFast on G0/1 allows immediate transition to forwarding state, and BPDU Guard protects against BPDU attacks by disabling the port if a BPDU is received.

    Clue confirmation

    The clue word "immediately / without restart" in the question point toward this answer.

    Related concept

    Access ports place end devices into a single VLAN.

  • Configure 'spanning-tree vlan 1 priority 4096' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree guard root'.

    Why it's wrong here

    This is incorrect because setting the priority to 4096 is not the standard method; the 'root primary' command is preferred. Additionally, 'spanning-tree guard root' is used to protect the root bridge, not to prevent BPDU attacks on access ports.

  • Configure 'spanning-tree vlan 1 root secondary' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'.

    Why it's wrong here

    This is incorrect because 'spanning-tree vlan 1 root secondary' sets the priority to 28672, which is intended for backup root, not primary. It will not make SW1 the root bridge if SW2 has a lower priority.

  • Configure 'spanning-tree vlan 1 priority 32768' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree bpdufilter enable'.

    Why it's wrong here

    This is incorrect because setting the priority to 32768 is the default priority and will not make SW1 root. BPDU filter prevents sending BPDUs but does not protect against BPDU attacks; it can actually cause loops if misapplied.

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.

Configure 'spanning-tree vlan 1 root primary' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'.Correct answer

Why this is correct

This is correct because 'spanning-tree vlan 1 root primary' sets the bridge priority to 24576 (or lower if needed) to ensure SW1 becomes root for VLAN 1. PortFast on G0/1 allows immediate transition to forwarding state, and BPDU Guard protects against BPDU attacks by disabling the port if a BPDU is received.

Configure 'spanning-tree vlan 1 priority 4096' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree guard root'.Wrong answer — click to see why

Why this is wrong here

The specific factual error: 'spanning-tree guard root' is a root guard feature, not BPDU guard. Also, manually setting priority to 4096 may not guarantee root if another switch has lower priority.

Why candidates choose this

Candidates might think setting a low priority manually is equivalent to 'root primary', and confuse root guard with BPDU guard.

Configure 'spanning-tree vlan 1 root secondary' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'.Wrong answer — click to see why

Why this is wrong here

The specific factual error: 'root secondary' is for backup root, not primary. It sets priority to 28672, which is higher than the default priority of 32768 but not low enough to become root if another switch has a lower priority.

Why candidates choose this

Candidates may confuse 'root primary' and 'root secondary', thinking 'secondary' might still become root if the current root fails, but the question asks to make SW1 root now.

Configure 'spanning-tree vlan 1 priority 32768' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree bpdufilter enable'.Wrong answer — click to see why

Why this is wrong here

The specific factual error: priority 32768 is default and does not change root status. BPDU filter is not a security feature against BPDU attacks; it suppresses BPDUs entirely.

Why candidates choose this

Candidates might think any low priority works, and confuse BPDU filter with BPDU guard. BPDU filter is sometimes used on access ports but does not provide the same protection.

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?”

Common exam traps

Common exam trap: an active trunk can still block the VLAN you need

A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.

Trap categories for this question

  • Command / output trap

    This is incorrect because setting the priority to 4096 is not the standard method; the 'root primary' command is preferred. Additionally, 'spanning-tree guard root' is used to protect the root bridge, not to prevent BPDU attacks on access ports.

Detailed technical explanation

How to think about this question

VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.

KKey Concepts to Remember

  • Access ports place end devices into a single VLAN.
  • Trunk ports carry multiple VLANs between switches.
  • Allowed VLAN lists decide which VLANs can cross a trunk.
  • Native VLAN mismatch can create confusing symptoms.

TExam Day Tips

  • Use show vlan brief to verify access VLANs.
  • Use show interfaces trunk to verify trunk state and allowed VLANs.
  • Do not treat every same-VLAN issue as a routing problem.

Key takeaway

A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.

Real-world example

How this comes up in practice

A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.

Visual reference

SW1 Root Bridge SW2 SW3 BLK DP DP RP RP STP blocks one link to prevent loops DP = Designated Port RP = Root Port BLK = Blocked

What to study next

Got this wrong? Here's your next step.

Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.

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Related 200-301 practice-question pages

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FAQ

Questions learners often ask

What does this 200-301 question test?

Switching and Network Access — This question tests Switching and Network Access — Access ports place end devices into a single VLAN..

What is the correct answer to this question?

The correct answer is: Configure 'spanning-tree vlan 1 root primary' globally, and on interface G0/1 configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'. — The 'spanning-tree vlan 1 root primary' command reduces the bridge priority to 24576 (or lower) to ensure SW1 becomes root for VLAN 1. PortFast on G0/1 speeds up access port convergence, and BPDU Guard protects against rogue switches by disabling the port upon BPDU reception.

What should I do if I get this 200-301 question wrong?

Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.

Are there clue words in this question I should notice?

Yes — watch for: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.

What is the key concept behind this question?

Access ports place end devices into a single VLAN.

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Same concept, more angles

1 more ways this is tested on 200-301

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. You are connected to SW1 via console. SW1 is a Layer 2 switch connected to two other switches (SW2 and SW3) via trunk links. The network administrator wants to ensure that SW1 becomes the root bridge for VLAN 10 and VLAN 20. Currently, SW2 is the root for both VLANs. Configure SW1 to become the root bridge for these VLANs using the Cisco-recommended macro STP commands.

medium
  • A.spanning-tree vlan 10 root primary; spanning-tree vlan 20 root primary
  • B.spanning-tree vlan 10 root secondary; spanning-tree vlan 20 root secondary
  • C.spanning-tree vlan 10 priority 4096; spanning-tree vlan 20 priority 4096
  • D.spanning-tree vlan 10 root; spanning-tree vlan 20 root

Why A: The 'spanning-tree vlan <vlan> root primary' command is the Cisco-recommended macro that sets the bridge priority to 24576, which is lower than the default 32768, making SW1 the root bridge for those VLANs. Option A correctly uses this macro. Option C, while it could achieve the same goal by setting priority to 4096, is not the macro command and would be considered a static configuration; the question specifically asks for the appropriate macro commands. Option B sets priority to 28672 as a secondary root, and Option D is invalid syntax.

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Last reviewed: Jun 7, 2026

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