- A
The computer's NIC is faulty.
Why wrong: The NIC worked at the previous desk, so it is unlikely to be the issue.
- B
The patch cable is not a crossover cable.
Why wrong: Modern NICs auto-MDIX, so crossover cables are not needed.
- C
The wall jack is terminated incorrectly.
An incorrect termination at the new jack would prevent a link, explaining the no-link light.
- D
The switch port is administratively down.
Why wrong: While possible, it is less likely than a physical termination issue, especially if other ports work.
Question 882 of 1,020
Troubleshooting No Link Light Due to Faulty Wall Jack Termination
This 220-1201 practice question tests your understanding of cabling. 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 computer connected to a wall jack works fine, but when they move the computer to a different desk and plug into a different wall jack, there is no network connectivity. The switch port shows no link light. 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.
Quick Answer
The answer is a faulty wall jack termination. When a computer works on one jack but shows no link light on another, the issue is almost always a physical wiring problem at the new location, not the device or switch port. A link light requires a complete electrical circuit through all eight wires of the Ethernet cable; if the wall jack is terminated incorrectly—such as using the wrong wiring standard (T568A vs. T568B) or failing to fully punch down a pair—the circuit breaks, and the switch cannot establish a link. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of physical layer troubleshooting, specifically that a missing link light points to a Layer 1 fault. A common trap is blaming the patch cable or switch port, but the key clue is that the problem follows the wall jack, not the computer. Remember: no link light means no electrical continuity—check the termination first, not the hardware.
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 wall jack is terminated incorrectly.
The most likely cause is that the wall jack at the new desk is terminated incorrectly, such as a miswired T568A/T568B standard or a broken punch-down connection. Since the computer works at the original jack and the switch port shows no link light, the issue is isolated to the new cabling path, not the NIC or switch configuration. Incorrect termination can cause a physical layer failure, preventing the switch from detecting a carrier signal.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 computer's NIC is faulty.
Why it's wrong here
The NIC worked at the previous desk, so it is unlikely to be the issue.
- ✗
The patch cable is not a crossover cable.
Why it's wrong here
Modern NICs auto-MDIX, so crossover cables are not needed.
- ✓
The wall jack is terminated incorrectly.
Why this is correct
An incorrect termination at the new jack would prevent a link, explaining the no-link light.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The switch port is administratively down.
Why it's wrong here
While possible, it is less likely than a physical termination issue, especially if other ports work.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The exam often tests the misconception that a faulty NIC or crossover cable is the cause, but the key clue is that the computer works at one jack and fails at another, isolating the problem to the new cabling path rather than the endpoint or switch configuration.
Detailed technical explanation
How to think about this question
In structured cabling, a wall jack termination must follow either T568A or T568B pinout precisely; a miswire (e.g., split pairs or reversed pins) can cause excessive crosstalk or open circuits, preventing link negotiation. The switch port's link light relies on a successful auto-negotiation pulse (FLP bursts) at Layer 1; if the termination is faulty, no pulses are exchanged, and the port remains in a 'no link' state. Real-world scenarios often involve punch-down tool errors or damaged keystone jacks that pass a continuity test but fail under actual signal frequencies.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Cabling — This question tests Cabling — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The wall jack is terminated incorrectly. — The most likely cause is that the wall jack at the new desk is terminated incorrectly, such as a miswired T568A/T568B standard or a broken punch-down connection. Since the computer works at the original jack and the switch port shows no link light, the issue is isolated to the new cabling path, not the NIC or switch configuration. Incorrect termination can cause a physical layer failure, preventing the switch from detecting a carrier signal.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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