The answer is TIA/EIA-568, the standard that defines proper wiring pinouts and performance requirements for twisted-pair cabling. An open pair violates this standard because it breaks the required electrical continuity across all four pairs, which is essential for reliable data transmission. Even though solid link lights on the PC and switch indicate basic connectivity on some pairs, the open pair causes intermittent drops when the network attempts to use that specific pair for data, leading to signal degradation and periodic failures. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding that link lights alone do not guarantee full cable integrity—a common trap is assuming solid lights mean the cable is fully functional. A useful memory tip: think of the “four-pair rule” under TIA/EIA-568—if any pair is open, the cable is out of spec, just like a missing lane on a highway causes traffic jams.
N10-009 Network Troubleshooting Practice Question
This N10-009 practice question tests your understanding of network troubleshooting. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 user reports intermittent connectivity issues. The technician notices that the link lights on both the PC and the switch are solid, but the user experiences periodic drops. The technician runs a cable test and finds that one pair of wires is open. Which standard is the cable likely violating?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
TIA/EIA-568
The TIA/EIA-568 standard specifies the wiring pinouts and performance requirements for twisted-pair cabling, including that all four pairs must be properly terminated and continuous. An open pair violates this standard because it breaks the required electrical continuity, leading to signal degradation and intermittent connectivity. The solid link lights indicate basic electrical connectivity on some pairs, but the open pair causes periodic drops when the network attempts to use that pair for data transmission.
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.
✓
TIA/EIA-568
Why this is correct
TIA/EIA-568 is the standard for commercial building telecommunications cabling; an open pair violates its requirements.
Related concept
Read the scenario before looking for a memorised answer.
✗
IEEE 802.3
Why it's wrong here
IEEE 802.3 defines Ethernet physical layer standards, but the specific wiring pinout is covered by TIA/EIA-568.
✗
ISO 9001
Why it's wrong here
ISO 9001 is a quality management standard, not a cabling specification.
✗
RFC 1918
Why it's wrong here
RFC 1918 defines private IP address ranges, not physical cabling standards.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates see 'link lights solid' and assume the cable is fully functional, but solid link lights only indicate that at least one pair (or the necessary pairs for the negotiated speed) is electrically connected, not that all pairs meet the TIA/EIA-568 standard for the expected speed.
Detailed technical explanation
How to think about this question
In 1000BASE-T (Gigabit Ethernet), all four pairs are used simultaneously for bidirectional data transmission using echo cancellation and hybrid circuits. An open pair causes the link to fall back to a lower speed (e.g., 100BASE-TX, which uses only two pairs) or results in CRC errors and retransmissions, manifesting as intermittent drops. Cable testers detect opens by sending a time-domain reflectometer (TDR) pulse and measuring the reflection; an open pair shows a reflection at the break point.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Troubleshooting — This question tests Network Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: TIA/EIA-568 — The TIA/EIA-568 standard specifies the wiring pinouts and performance requirements for twisted-pair cabling, including that all four pairs must be properly terminated and continuous. An open pair violates this standard because it breaks the required electrical continuity, leading to signal degradation and intermittent connectivity. The solid link lights indicate basic electrical connectivity on some pairs, but the open pair causes periodic drops when the network attempts to use that pair for data transmission.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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