- A
A
Why wrong: 10 Gigabit Ethernet is widely supported and not the cause of this specific issue.
- B
B
Why wrong: While a faulty fiber cable could cause general failures, the pattern of small transfers working and large transfers failing points to an MTU issue.
- C
C
An intermediate device with a standard MTU will drop large frames, causing jumbo frame traffic to fail.
- D
D
Why wrong: TCP window size affects throughput but not the ability to transfer large files at all; small transfers would also fail if window size were severely misconfigured.
Question 163 of 520
Troubleshooting Jumbo Frame MTU Mismatch: Why Large Files Fail
This N10-009 practice question tests your understanding of networking concepts. 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 network engineer is troubleshooting connectivity issues between two data center switches that are configured to support jumbo frames with an MTU of 9000. The link is a 10 Gigabit Ethernet fiber connection. Large file transfers fail, but small transfers succeed. 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 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
✓
C
The most likely cause is that an intermediate device (such as a router or another switch) along the Layer 2 path is not configured for jumbo frames and has a standard MTU of 1500. Since both end switches support an MTU of 9000, large frames are sent but are dropped when they reach the intermediate device that cannot handle them. Small frames (≤1500 bytes) pass through successfully because they fit within the standard MTU.
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.
- ✗
A
Why it's wrong here
10 Gigabit Ethernet is widely supported and not the cause of this specific issue.
When this WOULD be correct
Option A would be correct in a scenario where one switch is configured for jumbo frames (MTU 9000) and the other is set to the default MTU (1500), causing large frame fragmentation or drops.
- ✗
B
Why it's wrong here
While a faulty fiber cable could cause general failures, the pattern of small transfers working and large transfers failing points to an MTU issue.
When this WOULD be correct
If the question described intermittent connectivity or errors on a fiber link with both small and large transfers failing, then fiber attenuation or dirty connectors could be the cause, making B correct.
- ✓
C
Why this is correct
An intermediate device with a standard MTU will drop large frames, causing jumbo frame traffic to fail.
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.
- ✗
D
Why it's wrong here
TCP window size affects throughput but not the ability to transfer large files at all; small transfers would also fail if window size were severely misconfigured.
When this WOULD be correct
In a scenario where a network engineer is troubleshooting intermittent connectivity and finds that disabling jumbo frames resolves the issue, option D (if it were 'Disable jumbo frames on both switches') would be correct to restore connectivity at the cost of performance.
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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓CCorrect answer▾
Why this is correct
An intermediate device with a standard MTU will drop large frames, causing jumbo frame traffic to fail.
✗AWrong answer — click to see why▾
Why this is wrong here
Option A is not a valid answer choice in this question; the actual options are not provided, but assuming 'A' refers to a common distractor like 'MTU mismatch', that would be incorrect because both switches are configured for jumbo frames with MTU 9000, so MTU mismatch is not the issue.
★ When this WOULD be the correct answer
Option A would be correct in a scenario where one switch is configured for jumbo frames (MTU 9000) and the other is set to the default MTU (1500), causing large frame fragmentation or drops.
Why candidates choose this
Candidates often default to 'MTU mismatch' as a common cause of large file transfer failures, without verifying that both devices are consistently configured.
✗BWrong answer — click to see why▾
Why this is wrong here
Option B is not specified, but assuming it refers to a common incorrect cause like 'CRC errors' or 'fiber attenuation', these would not selectively affect large transfers while allowing small ones; jumbo frame issues typically stem from MTU mismatch or switch configuration.
★ When this WOULD be the correct answer
If the question described intermittent connectivity or errors on a fiber link with both small and large transfers failing, then fiber attenuation or dirty connectors could be the cause, making B correct.
Why candidates choose this
Candidates may confuse general physical layer issues with MTU-specific problems, or they might recall that fiber problems can cause packet loss, but fail to recognize that MTU mismatch only impacts large frames.
✗DWrong answer — click to see why▾
Why this is wrong here
Option D is not provided in the question, so it cannot be analyzed. The correct answer is C, which likely refers to a mismatch in MTU settings or jumbo frame configuration across the path, causing large frames to be dropped.
★ When this WOULD be the correct answer
In a scenario where a network engineer is troubleshooting intermittent connectivity and finds that disabling jumbo frames resolves the issue, option D (if it were 'Disable jumbo frames on both switches') would be correct to restore connectivity at the cost of performance.
Why candidates choose this
Without the actual text of option D, it's impossible to determine why it might be tempting. Typically, wrong options in such questions might suggest incorrect causes like faulty cables or duplex mismatches, which candidates might choose due to common troubleshooting experience.
Analysis generated from the official N10-009blueprint 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
The trap here is that candidates often assume a physical layer issue (like a bad cable or transceiver) when the symptom is selective failure based on packet size, but the real cause is an MTU mismatch, which is a Layer 2 configuration problem.
Detailed technical explanation
How to think about this question
Jumbo frames are Ethernet frames with a payload larger than 1500 bytes, up to 9000 bytes. The MTU is configured on each interface; if a switch receives a frame larger than its MTU, it drops it silently (no ICMP notification in Layer 2). In a data center, jumbo frames reduce CPU overhead by enabling larger data chunks per packet, but all devices in the path must support and be configured for the same MTU. A common real-world scenario is a storage network (e.g., iSCSI or NFS) where jumbo frames improve throughput, but a misconfigured switch causes partial failures.
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 practitioner preparing for the N10-009 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this N10-009 question test?
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: C — The most likely cause is that an intermediate device (such as a router or another switch) along the Layer 2 path is not configured for jumbo frames and has a standard MTU of 1500. Since both end switches support an MTU of 9000, large frames are sent but are dropped when they reach the intermediate device that cannot handle them. Small frames (≤1500 bytes) pass through successfully because they fit within the standard MTU.
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.
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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Last reviewed: Jun 11, 2026
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