The answer is the cable length exceeds the maximum specification for Ethernet. Cat6 cabling is officially rated for a maximum segment length of 100 meters, and at that exact distance, signal attenuation and crosstalk can cause the link to fail, especially when combined with Power over Ethernet demands that further degrade voltage over the run. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of Ethernet physical layer limitations, often appearing as a trap where a technician assumes a 100-meter run is acceptable without accounting for patch cables, poor termination, or environmental interference. A common memory tip is "100 meters is the limit, not a guarantee"—always leave a safety margin of a few meters for connectors and bends.
220-1201 Network Troubleshooting Practice Question
This 220-1201 practice question tests your understanding of network troubleshooting. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 technician is called to a warehouse where a newly installed IP camera shows 'No Signal' on the NVR. The camera is connected via a 100-meter Cat6 cable to a PoE switch. The switch port LED is off. 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
✓
The cable length exceeds the maximum specification for Ethernet.
This question tests knowledge of Ethernet cable length limits. Cat6 is rated for 100 meters; at exactly that distance, signal degradation can cause link failure. The PoE switch may not provide enough power over that distance, or the cable may be slightly too long.
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 camera's IP address is conflicting with another device.
Why it's wrong here
Incorrect; an IP conflict would not cause the switch port LED to be off.
✓
The cable length exceeds the maximum specification for Ethernet.
Why this is correct
Correct. 100 meters is the limit; at that length, signal loss can prevent link.
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 PoE switch does not support the camera's power requirement.
Why it's wrong here
Incorrect; the port LED would likely be on if power were the only issue, but no link indicates signal problem.
✗
The camera is configured for a different VLAN.
Why it's wrong here
Incorrect; VLAN misconfiguration would not cause the physical link LED to be off.
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: The cable length exceeds the maximum specification for Ethernet. — This question tests knowledge of Ethernet cable length limits. Cat6 is rated for 100 meters; at exactly that distance, signal degradation can cause link failure. The PoE switch may not provide enough power over that distance, or the cable may be slightly too long.
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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