- A
The PC's network cable is faulty.
Why wrong: While possible, the most likely cause is a configuration issue on the switch, especially since the phone works.
- B
The VoIP phone's passthrough port is disabled.
Why wrong: Most phones have the passthrough enabled by default. Disabling it would be an intentional change, not a common issue.
- C
The switch port is not configured for the data VLAN, so the PC cannot get an IP address.
Correct. VoIP phones often use separate VLANs. If the switch port only allows the voice VLAN, the PC's traffic is blocked. Configuring the port for both VLANs resolves this.
- D
The PC's network adapter is set to a static IP address that conflicts with the phone.
Why wrong: IP conflicts would cause issues for both devices, not just the PC. The phone works fine, so this is unlikely.
220-1201 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 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?
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 is not configured for the data VLAN, so the PC cannot get an IP address.
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.
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 PC's network cable is faulty.
Why it's wrong here
While possible, the most likely cause is a configuration issue on the switch, especially since the phone works.
- ✗
The VoIP phone's passthrough port is disabled.
Why it's wrong here
Most phones have the passthrough enabled by default. Disabling it would be an intentional change, not a common issue.
- ✓
The switch port is not configured for the data VLAN, so the PC cannot get an IP address.
Why this is correct
Correct. VoIP phones often use separate VLANs. If the switch port only allows the voice VLAN, the PC's traffic is blocked. Configuring the port for both VLANs resolves this.
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 PC's network adapter is set to a static IP address that conflicts with the phone.
Why it's wrong here
IP conflicts would cause issues for both devices, not just the PC. The phone works fine, so this is unlikely.
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 is not configured for the data VLAN, so the PC cannot get an IP address. — 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.
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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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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