CCNA Switching and Network Access Practice Question
Network Topology
You are connected to SW1. The network has three switches (SW1, SW2, SW3) running Rapid-PVST+. SW1 should be the root bridge for VLAN 10. PortFast and BPDU Guard must be enabled on all edge ports connected to end hosts. An err-disabled port (G0/1) has occurred due to a BPDU violation on an edge port. Recover the port and ensure it is configured correctly to prevent recurrence.
⚠ Common exam trap
The exam trap is that candidates may focus on recovering the port (shutdown/no shutdown) but forget to address why the BPDU was received. Simply re-enabling BPDU Guard or reapplying PortFast will not prevent recurrence. The key is to ensure the connected device is not sending BPDUs, either by removing it or reclassifying the port.
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
✓
Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then verify that the connected device is not a switch or remove it from the network.
The port Gi0/1 is in err-disabled state because BPDU Guard disabled it after receiving a BPDU on a PortFast edge port. First, shut down the interface and then re-enable it with 'no shutdown' to recover from err-disabled. However, to prevent recurrence, the root cause must be addressed: the connected device (likely another switch) should not be sending BPDUs on an edge port. Optionally, you can disable BPDU Guard on that specific port if it is not truly an edge port, but the task requires PortFast and BPDU Guard on edge ports. The correct fix is to ensure no BPDUs are sent from the downstream device or use 'spanning-tree bpduguard disable' on that port if it is not an edge port (but the task mandates BPDU Guard). Since the scenario requires BPDU Guard, the candidate should recover the port and then verify that the connected device is not a switch (or remove it from the topology).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree bpduguard disable' on the interface.
Why it's wrong here
This is incorrect because disabling BPDU Guard on the port would allow BPDUs to be received, which violates the requirement that BPDU Guard must be enabled on all edge ports. The port would remain vulnerable to BPDU attacks.
- ✗
Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable' on the interface.
Why it's wrong here
This is incorrect because the port already has PortFast and BPDU Guard enabled (as required). Re-enabling them does not address the root cause: the connected device is sending BPDUs. The port will go err-disabled again immediately after recovery.
- ✗
Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree guard root' on the interface.
Why it's wrong here
This is incorrect because Root Guard and BPDU Guard address different failure domains. Root Guard protects the Spanning Tree topology by preventing a designated port from becoming a root port when a superior BPDU arrives; it does not disable the port for merely receiving BPDUs. On an access port with PortFast and BPDU Guard enabled, the port is placed into err-disabled state upon receiving any BPDU, regardless of BPDU priority. Configuring 'spanning-tree guard root' would not prevent the err-disabled state, nor does it address the root cause that an unauthorized or unexpected device is sending BPDUs on an edge port. The port would still remain in err-disabled after the next BPDU reception.
- ✓
Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then verify that the connected device is not a switch or remove it from the network.
Why this is correct
This is correct because the port is err-disabled due to BPDU Guard. After recovering with 'shutdown' and 'no shutdown', the root cause must be addressed: the connected device is sending BPDUs, which should not happen on an edge port. Either the device is not an end host (e.g., it is another switch) and should be connected to a trunk port, or it is a rogue device that should be removed. This ensures BPDU Guard remains enabled and the port stays up.
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.
✓Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then verify that the connected device is not a switch or remove it from the network.Correct answer▾
Why this is correct
This is correct because the port is err-disabled due to BPDU Guard. After recovering with 'shutdown' and 'no shutdown', the root cause must be addressed: the connected device is sending BPDUs, which should not happen on an edge port. Either the device is not an end host (e.g., it is another switch) and should be connected to a trunk port, or it is a rogue device that should be removed. This ensures BPDU Guard remains enabled and the port stays up.
✗Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree bpduguard disable' on the interface.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that BPDU Guard should not be disabled on a port that is supposed to be an edge port with BPDU Guard enabled.
Why candidates choose this
Candidates may think that disabling BPDU Guard prevents the port from going err-disabled again, but this contradicts the requirement to keep BPDU Guard enabled.
✗Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable' on the interface.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that simply re-enabling the same features does not prevent recurrence; the source of BPDUs must be removed or the port must be reconfigured as a non-edge port.
Why candidates choose this
Candidates may think that re-applying the configuration ensures the port is correctly configured, but they overlook that the BPDU source is still present.
✗Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree guard root' on the interface.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that Root Guard and BPDU Guard serve different purposes; Root Guard does not stop BPDU Guard from disabling the port.
Why candidates choose this
Candidates may confuse Root Guard with BPDU Guard or think that any spanning-tree guard feature can solve the issue.
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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Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
Err-disabled
Err-disabled is a switch port state that occurs when the switch detects a critical error on that port and automatically shuts it down to protect the network.
Key term
Interface
An interface is a point of connection or interaction between two systems, devices, or software components that allows them to exchange information or signals.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.