Question 1hardmultiple choice
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- → When each wrong option would be correct
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Question 912 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: A network administrator is troubleshooting…
This 200-301 practice question tests your understanding of 200-301 exam topics. 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.
Exhibit
SwitchA# show interfaces gigabitethernet0/1
GigabitEthernet0/1 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 0011.2233.4401 (bia 0011.2233.4401)
Description: Link to SwitchB
Internet address is 192.168.1.1/30
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
1123 packets input, 123456 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
1123 packets output, 123456 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
SwitchA# show interfaces gigabitethernet0/1 counters errors
Port Align-Err FCS-Err Xmit-Err Rcv-Err UnderSize OutDiscards
Gi0/1 0 0 0 0 0 0
Port Single-Col Multi-Col Late-Col Excess-Col Carri-Sen Runts Giants
Gi0/1 0 0 0 0 0 0 0A network administrator is troubleshooting connectivity issues between two switches. Hosts connected to Switch A cannot ping hosts on Switch B. The link between the two switches shows as up/up on both ends, but the interface error counters are increasing rapidly. Based on the output from Switch A, what is the most likely cause of the problem?
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 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
✓
Change the duplex setting on SwitchA's interface to auto-negotiation.
The interface is up/up, but the error counters are all zero, indicating no physical layer errors. The problem is that the interface is configured for full-duplex while the remote switch (SwitchB) is likely set to auto-negotiation. This causes a duplex mismatch, leading to late collisions and performance issues. The correct fix is to set both sides to full-duplex manually. Option A is wrong because speed mismatch would typically cause the interface to be down. Option C is incorrect because CRC errors are not present. Option D is incorrect because the interface is up/up, so it is not administratively down.
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.
- ✗
Replace the faulty cable between the two switches.
Why it's wrong here
A faulty cable would typically cause physical layer errors such as CRC, runts, or giants, which are not present in the output.
- ✓
Change the duplex setting on SwitchA's interface to auto-negotiation.
Why this is correct
The interface is manually set to full-duplex, but the remote side is likely auto-negotiating. Setting both to auto or both to full-duplex resolves the mismatch.
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.
- ✗
Replace the SFP module on SwitchA's GigabitEthernet0/1 port.
Why it's wrong here
A faulty SFP would cause physical layer errors like CRC or alignment errors, which are absent in the output.
- ✗
Enable the interface with 'no shutdown' command.
Why it's wrong here
The interface is already up/up, so it is administratively enabled.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Change the duplex setting on SwitchA's interface to auto-negotiation.Correct answer▾
Why this is correct
The interface is manually set to full-duplex, but the remote side is likely auto-negotiating. Setting both to auto or both to full-duplex resolves the mismatch.
✗Replace the faulty cable between the two switches.Wrong answer — click to see why▾
Why this is wrong here
Cable issues would manifest as input errors or interface flapping, but the counters show zero errors.
✗Replace the SFP module on SwitchA's GigabitEthernet0/1 port.Wrong answer — click to see why▾
Why this is wrong here
No errors are reported, so the SFP is functioning correctly.
✗Enable the interface with 'no shutdown' command.Wrong answer — click to see why▾
Why this is wrong here
The 'show interface' output clearly shows the interface is up, so no shutdown is not needed.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
A faulty cable would typically cause physical layer errors such as CRC, runts, or giants, which are not present in the output.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Read the scenario before looking for a memorised answer.
What is the correct answer to this question?
The correct answer is: Change the duplex setting on SwitchA's interface to auto-negotiation. — The interface is up/up, but the error counters are all zero, indicating no physical layer errors. The problem is that the interface is configured for full-duplex while the remote switch (SwitchB) is likely set to auto-negotiation. This causes a duplex mismatch, leading to late collisions and performance issues. The correct fix is to set both sides to full-duplex manually. Option A is wrong because speed mismatch would typically cause the interface to be down. Option C is incorrect because CRC errors are not present. Option D is incorrect because the interface is up/up, so it is not administratively down.
What should I do if I get this 200-301 question wrong?
Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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.
About these practice questions
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