220-1101 Fluorescent lights are common sources of EMI. Practice Question
A user reports that their desktop computer intermittently loses network connectivity, especially when the nearby office printer starts printing. The link light on the NIC occasionally turns off during these events. The Ethernet cable runs near a fluorescent light fixture and a power cable. The technician has already replaced the Ethernet cable with a known-good Cat6 shielded cable, but the issue persists. Which of the following should the technician do NEXT?
⚠ Common exam trap
Many candidates assume replacing the cable with a shielded one automatically solves EMI issues, but they overlook that improper grounding or proximity to strong interference sources can still cause link drops, making environmental rerouting the correct next step.
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
✓
Ensure the Ethernet cable is not routed near sources of electromagnetic interference (EMI).
The issue persists even after replacing the cable with a known-good Cat6 shielded cable, indicating that the problem is not the cable itself but the environment. The Ethernet cable runs near a fluorescent light fixture and a power cable, both of which are common sources of electromagnetic interference (EMI). Since the link light turns off when the printer starts, the EMI from the printer or nearby sources is likely inducing noise on the cable, disrupting the signal. The next logical step is to reroute the cable away from these EMI sources, as shielding alone may not be sufficient if the interference is strong or the shield is not properly grounded.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Move the computer to a different electrical outlet.
Why it's wrong here
Moving the computer to a different electrical outlet changes only the AC power feed, not the route of the Ethernet cable or the proximate sources of interference. The link light turning off indicates a physical-layer issue on the network medium itself; a faulty outlet would more likely cause power instability or unintended shutdowns, not an intermittent network link drop. Unless the new outlet forces a completely different cable path, the same fluorescent ballast or power cable will continue to couple EMI into the twisted pair, leaving the problem unresolved.
- ✗
Replace the network interface card (NIC).
Why it's wrong here
The link light turning off suggests a physical layer issue. The NIC is not necessarily faulty; EMI can cause the link to drop. Replacing the NIC should be done after verifying cabling and environmental factors.
- ✓
Ensure the Ethernet cable is not routed near sources of electromagnetic interference (EMI).
Why this is correct
Fluorescent lights and power cables are common sources of EMI. Even with shielded cable, if routing is too close or shielding is not grounded, interference can cause intermittent link drops. Rerouting away from these sources is the logical next step.
- ✗
Update the NIC driver from the manufacturer's website.
Why it's wrong here
A NIC driver update addresses software-level bugs, protocol offload settings, or power management policies, but it cannot alter how the physical-layer transceiver interprets a corrupted signal caused by electromagnetic interference. The link LED on the NIC or switch is dropping, which means the electrical link synchronization is failing—a condition that occurs below the scope of the driver and is invisible to it. Even with the latest driver, the physical layer will still see excessive bit errors or loss of link if the Ethernet cable is picking up common-mode noise from nearby power lines or lighting. Driver updates are appropriate when the OS fails to recognize the NIC, sees frequent resets, or encounters protocol timeouts—not when the hardware link itself is toggling.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 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 220-1101 exam.