hardMultiple Choice
FC0-U71 Practice Question: After a network upgrade, a user reports that…
After a network upgrade, a user reports that their computer intermittently loses network connectivity. The link light remains on, but the activity light flashes rapidly and irregularly. What is the most likely cause?
⚠ Common exam trap
Watch out — candidates often confuse physical layer symptoms (bad cable) with Layer 2 or Layer 3 issues (IP conflict, driver corruption), assuming that intermittent connectivity must be a software or configuration problem rather than a hardware fault.
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
✓
Bad Ethernet cable
The intermittent connectivity with the link light on but the activity light flashing rapidly and irregularly is a classic symptom of a faulty or marginal Ethernet cable. A bad cable can cause excessive collisions or frame errors, leading to retransmissions that manifest as rapid, irregular activity light flashing while the physical link (link light) remains established. This is distinct from issues like IP conflicts or driver corruption, which typically do not produce this specific link/activity light behavior.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
IP address conflict
Why it's wrong here
An IP address conflict produces duplicate-address detection errors and total loss of connectivity, not rapid irregular activity-light flashing with the link light steady. That pattern indicates a duplex mismatch or cabling fault causing intermittent errors and retransmissions.
- ✓
Bad Ethernet cable
Why this is correct
A rapidly, irregularly flashing activity light with the link light still lit indicates frames are being transmitted but corrupted, typically by a damaged or poorly terminated cable. Replacing the Ethernet cable satisfies the intermittent-connectivity symptom without a link-state failure.
- ✗
Driver corruption
Why it's wrong here
Driver corruption typically produces a persistent failure or a device that never initialises, not the intermittent drops with a lit link light and irregular activity seen here. It would be the cause where the adapter fails after a driver or OS update and Device Manager shows an error code.
- ✗
Faulty NIC
Why it's wrong here
A faulty NIC usually extinguishes the link light or drops the connection entirely, whereas the stem shows a stable link with irregular activity, pointing to a duplicate address. It would be the cause where the adapter is undetected or the link light never illuminates.
Go deeper
Related to this question
About these practice questions
One of 988 original FC0-U71 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This FC0-U71 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 FC0-U71 exam.