- A
The router's firewall is blocking traffic between VLANs.
Why wrong: While possible, the question implies the router is set up for inter-VLAN routing. A firewall block would be a deliberate policy, not a common misconfiguration.
- B
The switch port connecting to the router is configured as an access port instead of a trunk.
An access port carries traffic for only one VLAN. For the router to receive traffic from multiple VLANs, the port must be a trunk port that tags frames with VLAN IDs.
- C
The default gateway for VLAN 20 is misconfigured.
Why wrong: Users can ping the default gateway, so the gateway is reachable. The issue is communication between VLANs, which requires the router to receive traffic from both.
- D
The switch has Spanning Tree Protocol enabled, blocking the link.
Why wrong: STP would block redundant links, not a single link to the router. If it were blocking, users in VLAN 10 might not even reach the gateway.
Quick Answer
The answer is that the switch port connecting to the router is configured as an access port instead of a trunk. For inter-VLAN routing to function, the router must receive traffic tagged with multiple VLAN IDs, which requires the switch port to operate in trunk mode, allowing all VLAN frames to pass. An access port, by contrast, strips VLAN tags and only carries traffic for a single VLAN, effectively isolating VLAN 20 from the router and breaking communication between VLANs. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your grasp of VLAN tagging and the physical link between a router and a managed switch—a common trap is assuming any port can route between VLANs. Remember the memory tip: “Trunk for trucking traffic between VLANs; access for a single address.”
220-1101 Common Networking Hardware Practice Question
This 220-1201 practice question tests your understanding of common networking hardware. 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.
A company's network uses a managed switch with VLANs. Users in VLAN 10 can ping the default gateway but cannot communicate with users in VLAN 20. The switch is connected to a router that handles inter-VLAN routing. What is the most likely misconfiguration?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The switch port connecting to the router is configured as an access port instead of a trunk.
This question tests understanding of inter-VLAN routing and trunk ports. For a router to route between VLANs, the switch port connecting to the router must be configured as a trunk port, allowing multiple VLAN tags. If the port is an access port, only one VLAN's traffic will pass. The correct answer is that the switch port connecting to the router is configured as an access port instead of a trunk.
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 router's firewall is blocking traffic between VLANs.
- ✓
The switch port connecting to the router is configured as an access port instead of a trunk.
Why this is correct
An access port carries traffic for only one VLAN. For the router to receive traffic from multiple VLANs, the port must be a trunk port that tags frames with VLAN IDs.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
- ✗
The default gateway for VLAN 20 is misconfigured.
Why it's wrong here
Users can ping the default gateway, so the gateway is reachable. The issue is communication between VLANs, which requires the router to receive traffic from both.
- ✗
The switch has Spanning Tree Protocol enabled, blocking the link.
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.
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 220-1201 questions on switching, trunking, and access-port configuration.
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Common Networking Hardware — This question tests Common Networking Hardware — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The switch port connecting to the router is configured as an access port instead of a trunk. — This question tests understanding of inter-VLAN routing and trunk ports. For a router to route between VLANs, the switch port connecting to the router must be configured as a trunk port, allowing multiple VLAN tags. If the port is an access port, only one VLAN's traffic will pass. The correct answer is that the switch port connecting to the router is configured as an access port instead of a trunk.
What should I do if I get this 220-1201 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 220-1201 questions on switching, trunking, and access-port configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 220-1201
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. A user reports that their VoIP phone works but the connected PC cannot access the network. The phone is connected to the wall jack, and the PC is connected to the phone's passthrough port. What is the most likely cause?
medium- A.The PC's network cable is faulty.
- B.The VoIP phone's passthrough port is disabled.
- ✓ C.The switch port is not configured for the data VLAN, so the PC cannot get an IP address.
- D.The PC's network adapter is set to a static IP address that conflicts with the phone.
Why C: This question tests understanding of VoIP phone pass-through ports and VLAN configuration. Many VoIP phones use a separate VLAN for voice and data. If the switch port is not configured for the data VLAN, the PC will not get network access.
Last reviewed: Jun 18, 2026
This 220-1201 practice question is part of Courseiva's free CompTIA 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 220-1201 exam.
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