The answer is that port 4 is assigned to a different VLAN without internet access. This is the most likely cause because VLANs create separate broadcast domains; while devices within the same VLAN can communicate locally, they require a router configured for inter-VLAN routing to reach external networks like the internet. If port 4’s VLAN lacks a default gateway or route to the router’s WAN interface, local traffic works but internet-bound packets are dropped. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of VLAN segmentation and router configuration—a common trap is assuming a solid link LED guarantees full connectivity, but it only confirms Layer 1 physical connection, not Layer 3 routing. Remember the memory tip: “Same VLAN, local LAN; different VLAN, need a plan”—meaning without a router linking VLANs, internet access fails.
220-1201 Network Troubleshooting Practice Question
This 220-1201 practice question tests your understanding of network troubleshooting. 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 small office uses a single router with four switch ports. Users on port 4 cannot access the internet, but they can communicate with each other. Port 4's LED is solid green. 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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Port 4 is assigned to a different VLAN without internet access.
This scenario tests understanding of VLANs and router configuration. Inter-VLAN routing is required for different VLANs to reach the internet. If port 4 is on a different VLAN without a route to the internet, users can talk locally but not externally.
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.
✗
Port 4 is administratively disabled.
Why it's wrong here
Incorrect; the LED is solid green, indicating the port is active.
✗
The cable on port 4 is faulty.
Why it's wrong here
Incorrect; a faulty cable would cause no link or errors, but users communicate locally.
✓
Port 4 is assigned to a different VLAN without internet access.
Why this is correct
Correct. VLAN misconfiguration can isolate the port from the router's default gateway.
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 router's DHCP pool is exhausted.
Why it's wrong here
Incorrect; users can communicate locally, so they have IP addresses.
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 220-1201 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 220-1201 questions on switching, trunking, and access-port configuration.
Network Troubleshooting — This question tests Network Troubleshooting — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Port 4 is assigned to a different VLAN without internet access. — This scenario tests understanding of VLANs and router configuration. Inter-VLAN routing is required for different VLANs to reach the internet. If port 4 is on a different VLAN without a route to the internet, users can talk locally but not externally.
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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