The answer is a missing `collect counter bytes` statement in the flow record definition. When a Flexible NetFlow byte counter configuration is incomplete, the router tracks packet counts but never populates the byte field, leaving it at zero in the cache even though flows are being exported. This happens because the flow record explicitly tells the router which counters to track; without the `collect counter bytes` command, the byte counter simply does not exist in the data structure. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding that NetFlow export success does not guarantee data completeness—a common trap is assuming that seeing export packets means all counters are working. The key distinction is that `collect counter packets` and `collect counter bytes` are separate, optional keywords within a flow record. A quick memory tip: think "packets without bytes is like a car without fuel—it moves but carries no weight."
300-410 NetFlow and Flexible NetFlow Practice Question
This 300-410 practice question tests your understanding of netflow and flexible netflow. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
An engineer notices that NetFlow export packets are being sent from a router but the collector reports missing data for certain flows. The engineer checks 'show ip flow export' and sees 'Exporting flows to 10.1.1.100 (2055)' with packets being sent. However, 'show flow monitor name MONITOR cache' shows many flows with zero byte counts. 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 flow record includes 'collect counter packets' but not 'collect counter bytes'.
If the flow record only collects packet counts but not byte counts, the byte counter will remain zero. This is a configuration error in the flow record definition.
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 flow exporter is using UDP port 2055, but the collector expects TCP.
Why it's wrong here
NetFlow uses UDP; TCP is not supported. This would not cause zero byte counts in the cache.
✓
The flow record includes 'collect counter packets' but not 'collect counter bytes'.
Why this is correct
Without 'collect counter bytes', the byte counter remains zero. The engineer must add this directive to the record.
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 router's CPU is overloaded, causing byte counters to not update.
Why it's wrong here
CPU overload would affect all counters, not just byte counters.
✗
The flow monitor is applied in egress direction, which does not support byte collection.
Why it's wrong here
Egress NetFlow supports byte collection; direction does not disable byte counters.
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.
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 300-410 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Identify which 300-410 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.
NetFlow and Flexible NetFlow — This question tests NetFlow and Flexible NetFlow — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The flow record includes 'collect counter packets' but not 'collect counter bytes'. — If the flow record only collects packet counts but not byte counts, the byte counter will remain zero. This is a configuration error in the flow record definition.
What should I do if I get this 300-410 question wrong?
Identify which 300-410 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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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. In Flexible NetFlow, what is the default 'collect counter bytes' setting for a flow record?
hard
A.Byte counters are collected by default.
B.Byte counters are never collected in Flexible NetFlow.
✓ C.Byte counters are collected only if the flow monitor includes the 'collect counter bytes' command.
D.Byte counters are collected by default only for IPv6 flows.
Why C: By default, byte counters are not collected unless explicitly configured with 'collect counter bytes' in the flow record.
Last reviewed: Jun 19, 2026
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