The answer is that the cable is cut or crushed in the conduit, breaking the secondary pairs. This is correct because 1000Base-T Ethernet requires all four twisted pairs (pins 1-2, 3-6, 4-5, and 7-8) for gigabit communication, while 100Base-TX only uses the primary pairs on pins 1, 2, 3, and 6. When a continuity test shows pins 4, 5, 7, and 8 are open but the primary pairs are intact, it indicates physical damage—likely a pinch or break in the conduit—that severed the secondary pairs, causing the switch to show 'No Link' because the link negotiation fails for gigabit speeds. On the CompTIA A+ Core 1 220-1201 exam, this tests your ability to map Ethernet pinout to cable faults; a common trap is assuming all pairs must fail for a link loss, but here the fault isolates to the unused pairs for 100Base-TX. A helpful memory tip: remember that gigabit needs all four pairs, so if only pins 1, 2, 3, and 6 pass, think “crushed in the conduit, not just a bad crimp.”
220-1101 Cabling Practice Question
This 220-1201 practice question tests your understanding of cabling. 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 technician is troubleshooting a network drop that was working yesterday but now shows 'No Link' on the switch port. The cable run is through a conduit in the wall. The technician tests the cable with a continuity tester and finds that pins 1, 2, 3, and 6 are good, but pins 4, 5, 7, and 8 show no continuity. What is the most likely cause?
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 cable is cut or crushed in the conduit, breaking the secondary pairs.
This question tests understanding of Ethernet pinout and fault isolation. The correct answer is that the cable is likely damaged or broken on the pairs used for 1000Base-T (all four pairs), but 100Base-TX only uses pairs 1-2 and 3-6. The symptom indicates a break in the cable affecting the secondary pairs.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 cable is only Cat5 and cannot support Gigabit.
Why it's wrong here
While Cat5 may not support Gigabit, the issue is a physical break, not a category limitation.
✗
The cable has a short circuit between pins 4 and 5.
Why it's wrong here
A short would show continuity, not an open circuit; the tester shows no continuity, indicating a break.
✓
The cable is cut or crushed in the conduit, breaking the secondary pairs.
Why this is correct
An open on pins 4-5 and 7-8 indicates a physical break in the cable that affects only those pairs, likely from damage in the conduit.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The wall jack is wired for T568A but the patch panel is T568B.
Why it's wrong here
Mismatched standards would cause a crossover, not an open circuit on specific pins.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
A short would show continuity, not an open circuit; the tester shows no continuity, indicating a break.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 220-1201 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
Cabling — This question tests Cabling — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The cable is cut or crushed in the conduit, breaking the secondary pairs. — This question tests understanding of Ethernet pinout and fault isolation. The correct answer is that the cable is likely damaged or broken on the pairs used for 1000Base-T (all four pairs), but 100Base-TX only uses pairs 1-2 and 3-6. The symptom indicates a break in the cable affecting the secondary pairs.
What should I do if I get this 220-1201 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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