The answer is a faulty or poor-quality Ethernet cable. CRC errors on an AP uplink almost always point to physical-layer degradation, where corrupted frames fail their cyclic redundancy check before reaching the switch. Since the AP connects via copper, a damaged cable, loose connector, or electromagnetic interference is the most likely culprit—not duplex mismatch (which causes alignment errors) or PoE issues (which cause power failures). On the ENCOR 350-401 exam, this question tests your ability to isolate Layer 1 problems from higher-layer symptoms; a common trap is blaming the AP’s radio or client load, but CRC errors are strictly a wired interface issue. Remember the mnemonic: “CRC = Cable, Radio, or Connector”—and for a copper uplink, always suspect the cable first.
CCNP Wireless Infrastructure Practice Question
This 350-401 practice question tests your understanding of wireless infrastructure. 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 network engineer is troubleshooting a wireless network where clients in a conference room experience intermittent connectivity. The engineer notices that the access point in that room is showing a high number of CRC errors on its uplink interface. The AP is connected to a Cisco 9300 switch via a copper cable. What is the most likely cause of the CRC errors?
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 Ethernet cable is faulty or of poor quality.
CRC errors typically indicate physical layer issues such as faulty cabling, bad connectors, or electromagnetic interference. Since the AP is connected via copper, a faulty cable is the most likely cause. Duplex mismatch would cause alignment errors, not just CRC. AP overload would not cause CRC errors on the uplink. PoE issues would cause power problems, not CRC errors.
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 AP is overloaded with too many clients.
Why it's wrong here
Incorrect because client overload would affect wireless performance, not cause CRC errors on the wired uplink.
✓
The Ethernet cable is faulty or of poor quality.
Why this is correct
Correct because CRC errors on a copper link are usually due to physical layer problems like faulty cables, bad connectors, or interference.
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 configured with a duplex mismatch.
Why it's wrong here
Incorrect because duplex mismatch typically causes runts, giants, and alignment errors, not just CRC errors.
✗
The AP is not receiving enough power from Power over Ethernet (PoE).
Why it's wrong here
Incorrect because insufficient PoE would cause the AP to reboot or not power on, not generate CRC errors.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 350-401 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.
What to study next
Got this wrong? Here's your next step.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Wireless Infrastructure — This question tests Wireless Infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Ethernet cable is faulty or of poor quality. — CRC errors typically indicate physical layer issues such as faulty cabling, bad connectors, or electromagnetic interference. Since the AP is connected via copper, a faulty cable is the most likely cause. Duplex mismatch would cause alignment errors, not just CRC. AP overload would not cause CRC errors on the uplink. PoE issues would cause power problems, not CRC errors.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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Question Discussion
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