CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 the multilayer switch SW1. Configure Root Guard on the designated port towards the access switch SW2, Loop Guard on the uplink port towards the distribution switch SW3, and BPDU Guard on the PortFast-enabled port connected to a workstation. After configuration, a superior BPDU is received on the designated port, causing it to be blocked by Root Guard. Later, a BPDU is received on the PortFast port, triggering err-disable state. Identify and resolve these issues.
SW1# show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address aaaa.bbbb.cccc
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address aaaa.bbbb.cccc
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20 sec
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi0/0 Desg FWD 4 128.1 P2p
Gi0/1 Desg FWD 4 128.2 P2p
Gi0/2 Desg FWD 4 128.3 P2p Edge
SW1# show running-config | section interface
interface GigabitEthernet0/0
description to SW2
switchport mode access
spanning-tree guard root
!
interface GigabitEthernet0/1
description to SW3
switchport mode trunk
spanning-tree guard loop
!
interface GigabitEthernet0/2
description to Workstation
switchport mode access
spanning-tree portfast
spanning-tree bpduguard enable
!
A
Remove Root Guard from interface Gi0/0 and re-enable interface Gi0/2 with a shutdown/no shutdown sequence.
Root Guard should not be applied to a designated port that may legitimately receive a superior BPDU; it should be applied to ports that should never become root ports. The superior BPDU on Gi0/0 indicates a valid root bridge with lower priority, so Root Guard must be removed. For Gi0/2, BPDU Guard correctly placed the port in err-disable state upon receiving a BPDU; the port must be manually re-enabled using shutdown/no shutdown after verifying the connected device.
B
Disable BPDU Guard on interface Gi0/2 and increase the root bridge priority on SW1 to prevent superior BPDUs.
Why wrong: This is incorrect because BPDU Guard is correctly configured on PortFast ports to prevent loops; disabling it would allow unauthorized switches to connect. Increasing root bridge priority would not resolve the Root Guard issue on Gi0/0, as Root Guard blocks any superior BPDU regardless of priority.
C
Apply Root Guard to interface Gi0/2 instead of Gi0/0 and configure Loop Guard on Gi0/0.
Why wrong: This is incorrect because Root Guard is not needed on a PortFast port; BPDU Guard already handles unauthorized BPDUs. Loop Guard is already correctly configured on the uplink port (Gi0/1) and should not be moved to Gi0/0, which is a designated port where Loop Guard could cause unnecessary blocking.
D
Remove Loop Guard from interface Gi0/1 and configure it on Gi0/0 instead, then re-enable Gi0/2 using the 'errdisable recovery cause bpduguard' command.
Why wrong: This is incorrect because Loop Guard is correctly applied to the uplink port (Gi0/1) to prevent loops caused by unidirectional links. Moving Loop Guard to Gi0/0 would not solve the Root Guard issue. While errdisable recovery can automatically re-enable the port, it does not address the root cause of why a BPDU was received on Gi0/2.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Remove Root Guard from interface Gi0/0 and re-enable interface Gi0/2 with a shutdown/no shutdown sequence.
The issue is that Root Guard was incorrectly applied to the designated port (Gi0/0) which should normally be the root port if a superior BPDU is received. Root Guard blocks the port when a superior BPDU arrives, but this is expected on a designated port; instead, Root Guard should be applied to ports that should never become root ports. In this scenario, the superior BPDU is legitimate (from a root bridge with lower priority), so Root Guard should be removed from Gi0/0. For the PortFast port (Gi0/2), BPDU Guard correctly err-disabled the port upon receiving a BPDU, indicating an unauthorized switch connection. To restore the port, you must shut/no shut the interface and then investigate why a BPDU was received. The solution involves removing Root Guard from Gi0/0 and re-enabling Gi0/2 after verifying the connecting device.
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.
✓
Remove Root Guard from interface Gi0/0 and re-enable interface Gi0/2 with a shutdown/no shutdown sequence.
Why this is correct
Root Guard should not be applied to a designated port that may legitimately receive a superior BPDU; it should be applied to ports that should never become root ports. The superior BPDU on Gi0/0 indicates a valid root bridge with lower priority, so Root Guard must be removed. For Gi0/2, BPDU Guard correctly placed the port in err-disable state upon receiving a BPDU; the port must be manually re-enabled using shutdown/no shutdown after verifying the connected device.
Related concept
Access ports place end devices into a single VLAN.
✗
Disable BPDU Guard on interface Gi0/2 and increase the root bridge priority on SW1 to prevent superior BPDUs.
Why it's wrong here
This is incorrect because BPDU Guard is correctly configured on PortFast ports to prevent loops; disabling it would allow unauthorized switches to connect. Increasing root bridge priority would not resolve the Root Guard issue on Gi0/0, as Root Guard blocks any superior BPDU regardless of priority.
✗
Apply Root Guard to interface Gi0/2 instead of Gi0/0 and configure Loop Guard on Gi0/0.
Why it's wrong here
This is incorrect because Root Guard is not needed on a PortFast port; BPDU Guard already handles unauthorized BPDUs. Loop Guard is already correctly configured on the uplink port (Gi0/1) and should not be moved to Gi0/0, which is a designated port where Loop Guard could cause unnecessary blocking.
✗
Remove Loop Guard from interface Gi0/1 and configure it on Gi0/0 instead, then re-enable Gi0/2 using the 'errdisable recovery cause bpduguard' command.
Why it's wrong here
This is incorrect because Loop Guard is correctly applied to the uplink port (Gi0/1) to prevent loops caused by unidirectional links. Moving Loop Guard to Gi0/0 would not solve the Root Guard issue. While errdisable recovery can automatically re-enable the port, it does not address the root cause of why a BPDU was received on Gi0/2.
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.
✓Remove Root Guard from interface Gi0/0 and re-enable interface Gi0/2 with a shutdown/no shutdown sequence.Correct answer▾
Why this is correct
Root Guard should not be applied to a designated port that may legitimately receive a superior BPDU; it should be applied to ports that should never become root ports. The superior BPDU on Gi0/0 indicates a valid root bridge with lower priority, so Root Guard must be removed. For Gi0/2, BPDU Guard correctly placed the port in err-disable state upon receiving a BPDU; the port must be manually re-enabled using shutdown/no shutdown after verifying the connected device.
✗Disable BPDU Guard on interface Gi0/2 and increase the root bridge priority on SW1 to prevent superior BPDUs.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that BPDU Guard should remain enabled on PortFast ports, and changing root bridge priority does not address the Root Guard misapplication.
Why candidates choose this
Candidates might think that adjusting priority could prevent the superior BPDU from being considered superior, but Root Guard blocks any BPDU with a lower bridge ID, not just those with lower priority.
✗Apply Root Guard to interface Gi0/2 instead of Gi0/0 and configure Loop Guard on Gi0/0.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that Root Guard is not appropriate for PortFast ports, and Loop Guard is already correctly placed on the uplink port.
Why candidates choose this
Candidates might confuse the purposes of Root Guard and Loop Guard, thinking that Root Guard should be on access ports and Loop Guard on designated ports.
✗Remove Loop Guard from interface Gi0/1 and configure it on Gi0/0 instead, then re-enable Gi0/2 using the 'errdisable recovery cause bpduguard' command.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that Loop Guard is already correctly placed, and automatic recovery does not replace the need to investigate the unauthorized BPDU on Gi0/2.
Why candidates choose this
Candidates might think that automatic recovery is a quick fix, but it bypasses the security purpose of BPDU Guard and does not resolve the misconfiguration of Root 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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: Remove Root Guard from interface Gi0/0 and re-enable interface Gi0/2 with a shutdown/no shutdown sequence. — The issue is that Root Guard was incorrectly applied to the designated port (Gi0/0) which should normally be the root port if a superior BPDU is received. Root Guard blocks the port when a superior BPDU arrives, but this is expected on a designated port; instead, Root Guard should be applied to ports that should never become root ports. In this scenario, the superior BPDU is legitimate (from a root bridge with lower priority), so Root Guard should be removed from Gi0/0. For the PortFast port (Gi0/2), BPDU Guard correctly err-disabled the port upon receiving a BPDU, indicating an unauthorized switch connection. To restore the port, you must shut/no shut the interface and then investigate why a BPDU was received. The solution involves removing Root Guard from Gi0/0 and re-enabling Gi0/2 after verifying the connecting device.
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.
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