The answer is that the configuration is correct and no changes are needed because each STP protection mechanism has been placed on the appropriate port type for its function. Root Guard is correctly applied to the designated downstream port (G0/1) to block a superior BPDU from a rogue switch, preventing it from becoming root, while Loop Guard is properly placed on the root port (G0/0) to detect a unidirectional link failure and prevent an STP loop if BPDUs cease. BPDU Guard is correctly enabled on the PortFast-configured access port (G0/2), which will err-disable the port upon receiving any BPDU. On the CCNA 200-301 v2 exam, this tests your ability to map each guard to its correct port role: Root Guard on designated ports, Loop Guard on root or alternate ports, and BPDU Guard only on PortFast access ports. A common trap is applying Root Guard to a root port or Loop Guard to a designated port, which would be ineffective or cause unintended blocking. Remember the mnemonic: "Root on Designated, Loop on Root, BPDU on Fast."
CCNA Switching and Network Access Practice Question
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
You are connected to R1, a multilayer switch acting as the STP root for VLAN 10. Configure Root Guard on the designated port facing a downstream switch to prevent a rogue switch from becoming root. Also, enable Loop Guard on the uplink port to prevent STP loops, and configure BPDU Guard on a PortFast-enabled access port. Ensure that if a superior BPDU is received on the Root Guard port, it is blocked, and if a BPDU is received on the BPDU Guard port, it goes err-disabled.
The configuration is correct; no changes are needed.
Root Guard on G0/1 (designated port) blocks superior BPDUs, Loop Guard on G0/0 (root port) prevents loops if BPDUs stop, and BPDU Guard on G0/2 (PortFast access port) err-disables on BPDU reception. All features are correctly applied per best practices.
B
Root Guard should be applied on G0/0 instead of G0/1, and Loop Guard on G0/1 instead of G0/0.
Why wrong: This is incorrect because Root Guard is intended for designated ports (like G0/1), not root ports. Loop Guard is intended for root or alternate ports, not designated ports. Swapping them would misapply the protections.
C
BPDU Guard should be configured on G0/1 instead of G0/2, and Loop Guard should be removed from G0/0.
Why wrong: This is incorrect because BPDU Guard is for access ports with PortFast, not for trunk or designated ports. Loop Guard is correctly applied on the root port (G0/0) to prevent loops if BPDUs stop arriving.
D
Root Guard should be applied on G0/2 instead of G0/1, and BPDU Guard should be removed from G0/2.
Why wrong: This is incorrect because Root Guard is not appropriate for an access port; it is for designated ports on trunks or inter-switch links. BPDU Guard is correctly used on PortFast access ports to protect against rogue BPDUs.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The configuration is correct; no changes are needed.
R1 is the STP root for VLAN 10. The downstream port (G0/1) is a designated port, so Root Guard is correctly applied to prevent a superior BPDU from being accepted. The uplink port (G0/0) is a root port, so Loop Guard should be applied there to prevent an STP loop if BPDUs stop arriving. The access port (G0/2) has PortFast and BPDU Guard enabled, which will err-disable the port if a BPDU is received. The current configuration is correct; no changes are needed. If a superior BPDU arrives on G0/1, Root Guard will block the port. If a BPDU arrives on G0/2, BPDU Guard will err-disable it.
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.
✓
The configuration is correct; no changes are needed.
Why this is correct
Root Guard on G0/1 (designated port) blocks superior BPDUs, Loop Guard on G0/0 (root port) prevents loops if BPDUs stop, and BPDU Guard on G0/2 (PortFast access port) err-disables on BPDU reception. All features are correctly applied per best practices.
Related concept
Access ports place end devices into a single VLAN.
✗
Root Guard should be applied on G0/0 instead of G0/1, and Loop Guard on G0/1 instead of G0/0.
Why it's wrong here
This is incorrect because Root Guard is intended for designated ports (like G0/1), not root ports. Loop Guard is intended for root or alternate ports, not designated ports. Swapping them would misapply the protections.
✗
BPDU Guard should be configured on G0/1 instead of G0/2, and Loop Guard should be removed from G0/0.
Why it's wrong here
This is incorrect because BPDU Guard is for access ports with PortFast, not for trunk or designated ports. Loop Guard is correctly applied on the root port (G0/0) to prevent loops if BPDUs stop arriving.
✗
Root Guard should be applied on G0/2 instead of G0/1, and BPDU Guard should be removed from G0/2.
Why it's wrong here
This is incorrect because Root Guard is not appropriate for an access port; it is for designated ports on trunks or inter-switch links. BPDU Guard is correctly used on PortFast access ports to protect against rogue BPDUs.
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.
✓The configuration is correct; no changes are needed.Correct answer▾
Why this is correct
Root Guard on G0/1 (designated port) blocks superior BPDUs, Loop Guard on G0/0 (root port) prevents loops if BPDUs stop, and BPDU Guard on G0/2 (PortFast access port) err-disables on BPDU reception. All features are correctly applied per best practices.
✗Root Guard should be applied on G0/0 instead of G0/1, and Loop Guard on G0/1 instead of G0/0.Wrong answer — click to see why▾
Why this is wrong here
Root Guard is only effective on designated ports; applying it to a root port would not prevent a rogue switch from becoming root. Loop Guard on a designated port is unnecessary and could cause false positives.
Why candidates choose this
Candidates often confuse which STP protection goes on which port type, thinking Root Guard should be on the root port to protect it, but it actually protects downstream designated ports.
✗BPDU Guard should be configured on G0/1 instead of G0/2, and Loop Guard should be removed from G0/0.Wrong answer — click to see why▾
Why this is wrong here
BPDU Guard on a trunk port would err-disable it upon receiving a BPDU, which is normal for trunk ports. Loop Guard on the root port is essential for loop prevention; removing it would leave the network vulnerable.
Why candidates choose this
Candidates might think BPDU Guard should be on all ports to prevent BPDU attacks, but it is specifically for PortFast-enabled access ports. They may also underestimate the importance of Loop Guard on root ports.
✗Root Guard should be applied on G0/2 instead of G0/1, and BPDU Guard should be removed from G0/2.Wrong answer — click to see why▾
Why this is wrong here
Root Guard on an access port would block the port if a superior BPDU is received, but access ports should not receive BPDUs if PortFast is enabled. BPDU Guard already handles that by err-disabling the port.
Why candidates choose this
Candidates might think Root Guard provides additional protection on access ports, but it is redundant and misapplied. They may also confuse the purpose of Root Guard and BPDU Guard.
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.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
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.
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: The configuration is correct; no changes are needed. — R1 is the STP root for VLAN 10. The downstream port (G0/1) is a designated port, so Root Guard is correctly applied to prevent a superior BPDU from being accepted. The uplink port (G0/0) is a root port, so Loop Guard should be applied there to prevent an STP loop if BPDUs stop arriving. The access port (G0/2) has PortFast and BPDU Guard enabled, which will err-disable the port if a BPDU is received. The current configuration is correct; no changes are needed. If a superior BPDU arrives on G0/1, Root Guard will block the port. If a BPDU arrives on G0/2, BPDU Guard will err-disable it.
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.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
About these practice questions
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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 R1, a multilayer switch acting as the STP root for VLAN 10. Configure Root Guard on port GigabitEthernet0/1 (designated port) to protect against superior BPDUs from an unauthorized switch, Loop Guard on uplink GigabitEthernet0/2 to prevent loops, and BPDU Guard on PortFast-enabled GigabitEthernet0/3. After configuration, a superior BPDU arrives on G0/1, blocking the port; verify the Root Guard state and ensure BPDU Guard triggers err-disable on G0/3.
hard
✓ A.G0/1 is in root-inconsistent state; G0/3 is in err-disabled state.
B.G0/1 is in blocking state; G0/3 is in err-disabled state.
C.G0/1 is in root-inconsistent state; G0/3 is in blocking state.
D.G0/1 is in err-disabled state; G0/3 is in root-inconsistent state.
Why A: Root Guard is needed on the designated port (G0/1) to prevent an unauthorized switch from becoming root by sending superior BPDUs. Loop Guard on the uplink (G0/2) prevents loops if BPDUs stop arriving. BPDU Guard on PortFast ports (G0/3) immediately err-disables them upon BPDU reception. The configuration uses 'spanning-tree guard root' on G0/1, 'spanning-tree guard loop' on G0/2, and 'spanning-tree bpduguard enable' on G0/3. Verification shows G0/1 blocked by root-inconsistent state and G0/3 in err-disabled state.
Variation 2. You are connected to R1, a multilayer switch acting as the STP root for VLAN 10. Configure Root Guard on port GigabitEthernet0/1 (designated port) to protect against superior BPDUs from an unauthorized switch, Loop Guard on uplink GigabitEthernet0/2 to prevent forwarding loops on unidirectional links, and BPDU Guard on PortFast-enabled GigabitEthernet0/3 to shut down the port if a BPDU is received. After configuration, troubleshoot the scenario: a superior BPDU is received on G0/1, causing it to be blocked by Root Guard, and an unauthorized switch sends a BPDU to G0/3, placing it in err-disable state. Verify the final configuration and state.
hard
✓ A.[CORRECT] Root Guard on G0/1 is correctly configured; when a superior BPDU is received, the port is placed into a root-inconsistent state (BKN* in show spanning-tree) to prevent the switch from becoming root. Loop Guard on G0/2 prevents loops if BPDUs stop arriving due to a unidirectional link. BPDU Guard on G0/3, combined with PortFast, err-disables the port upon receiving any BPDU, as shown by the err-disabled status. To recover, the administrator must manually re-enable the interface after removing the offending device. No additional configuration is required; the existing commands are correct and produce the expected behavior.
B.Root Guard on G0/1 is incorrectly configured; it should be configured on the root port, not the designated port. Loop Guard on G0/2 is correctly configured. BPDU Guard on G0/3 is correctly configured, but the port should automatically recover from err-disable state after a timeout.
C.Root Guard on G0/1 is correctly configured. Loop Guard on G0/2 is incorrectly configured because Loop Guard should be applied to root ports, not uplink ports. BPDU Guard on G0/3 is correctly configured, but the port should be in a blocking state, not err-disabled.
D.Root Guard on G0/1 is correctly configured. Loop Guard on G0/2 is correctly configured. BPDU Guard on G0/3 is incorrectly configured because BPDU Guard should be applied to trunk ports, not access ports, and the port should be placed in a root-inconsistent state.
Why A: The scenario demonstrates three STP protection mechanisms. Root Guard on G0/1 is correctly configured; when a superior BPDU is received, the port is placed into a root-inconsistent state (BKN* in show spanning-tree) to prevent the switch from becoming root. Loop Guard on G0/2 prevents loops if BPDUs stop arriving due to a unidirectional link. BPDU Guard on G0/3, combined with PortFast, err-disables the port upon receiving any BPDU, as shown by the err-disabled status. To recover, the administrator must manually re-enable the interface after removing the offending device. No additional configuration is required; the existing commands are correct and produce the expected behavior.
Last reviewed: Jun 6, 2026
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