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FC0-U71 Practice Question: A server in a data center is running a critical…
A server in a data center is running a critical application. The server is connected to a managed switch via two network cables for redundancy (link aggregation). Recently, the server experienced intermittent connectivity issues. The network logs show that every few hours, one of the links goes down and then comes back up within a minute. The other link remains up. The server's team reports no errors in the server logs. What is the most likely cause of this issue?
⚠ Common exam trap
Watch out — candidates often assume software or configuration issues (like broadcast storms or adapter overheating) when the symptom of a single link flapping in a LAG points directly to a physical-layer problem with that specific cable, not a systemic or hardware-wide 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
✓
The network cable is poorly terminated
A poorly terminated cable can cause intermittent physical-layer issues such as impedance mismatches or partial breaks, which lead to link flaps (link down/up events) without generating errors in the server's operating system logs. In a link aggregation group (LAG) using LACP or static aggregation, a single faulty cable will cause only that link to drop, while the other link continues to carry traffic, matching the described symptom of one link cycling every few hours.
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 switch's uplink port is faulty
Why it's wrong here
A faulty uplink port would disrupt all traffic traversing the switch, not repeatedly bounce a single member link while the other remains up. It is tempting because uplink faults do cause intermittent connectivity, and this would be the answer if the whole switch or its upstream path were dropping, rather than one LAG member.
- ✗
The switch is experiencing broadcast storms
Why it's wrong here
Broadcast storms flood all switch ports but do not selectively bounce one aggregated link while the other stays up. It is tempting because storms cause intermittent connectivity, yet the correct cause is a mismatched LACP configuration or flapping member link, which the logs would show as interface state changes.
- ✓
The network cable is poorly terminated
Why this is correct
A poorly terminated cable causes intermittent link flapping: the physical contact degrades, the link drops, then renegotiates within a minute while the second link stays up. Server logs show nothing because the fault sits at the physical layer, matching the symptoms.
- ✗
The server's network adapter is overheating
Why it's wrong here
Overheating would affect the adapter's traffic, not selectively drop one aggregated link while the other stays up and server logs stay clean. Thermal faults typically degrade both links or cause total failure. It is tempting because heat genuinely causes intermittent faults, and an overheating NIC would be the right diagnosis if both links flapped together under sustained load.
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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.