The answer is a poorly terminated network cable, because this physical-layer fault causes intermittent impedance mismatches or partial breaks that trigger link flaps—where a single link in a link aggregation group repeatedly drops and recovers—without generating errors in the server’s operating system logs. In a link aggregation group using LACP or static aggregation, only the faulty link cycles, while the other link stays up, exactly matching the symptom of one link going down every few hours. On the CompTIA ITF+ FC0-U61 exam, this question tests your ability to distinguish physical-layer issues from software or configuration problems; a common trap is assuming the server logs would always record such faults, but physical-layer errors are invisible to the OS. Remember the memory tip: “Cable crimp, link limp”—a poor termination makes a single link in the bundle flap, while the bundle itself keeps running.
FC0-U61 Infrastructure Practice Question
This FC0-U61 practice question tests your understanding of 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 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?
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 network cable is poorly terminated
Option C is correct because 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.
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 switch's uplink port is faulty
Why it's wrong here
A faulty uplink would disrupt traffic for multiple devices, not just one server link.
✗
The switch is experiencing broadcast storms
Why it's wrong here
Broadcast storms would affect the entire network, not just one link on one server.
✓
The network cable is poorly terminated
Why this is correct
Poor termination can cause intermittent connectivity on a single cable.
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 server's network adapter is overheating
Why it's wrong here
Overheating would likely cause both interfaces to fail, not just one.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that 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.
Detailed technical explanation
How to think about this question
Link aggregation (IEEE 802.3ad) uses a hash algorithm (e.g., XOR of MAC addresses or IP addresses) to distribute frames across member links; a single link failure causes the hash to redistribute traffic to the remaining links, which is seamless but can cause temporary packet loss during the failover. A poorly terminated cable often exhibits intermittent open or short circuits due to crosstalk or poor contact, which triggers the switch's link beat detection (based on fast link pulses per 10/100/1000BASE-T) to declare the link down, then re-establish it when the electrical connection temporarily improves. In real-world data centers, this is a common issue with field-terminated RJ45 plugs that fail the TIA/EIA-568-B wiring standards, especially in high-vibration environments.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
Infrastructure — This question tests Infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The network cable is poorly terminated — Option C is correct because 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.
What should I do if I get this FC0-U61 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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Question Discussion
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