This N10-009 practice question tests your understanding of network operations. 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 network administrator needs to identify which application protocols are consuming the most bandwidth on the company WAN link. Which of the following tools should the administrator use?
NetFlow collects flow records that show application-level details such as protocol and port numbers, enabling bandwidth usage analysis per application.
B
Packet sniffer (e.g., tcpdump)
Why wrong: While a packet sniffer can capture full packets, it is heavy for long-term bandwidth analysis and does not aggregate data as effectively as NetFlow.
C
Port scanner (e.g., Nmap)
Why wrong: A port scanner identifies open ports on hosts but does not measure bandwidth consumption over time.
D
Bandwidth speed test
Why wrong: A speed test measures total throughput between two points, not application-level breakdown of bandwidth usage.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
NetFlow analyzer
A NetFlow analyzer is the correct tool because it collects flow-level metadata (e.g., source/destination IPs, ports, protocol, and byte counts) from routers or switches, enabling the administrator to identify which application protocols (via port/protocol analysis) are consuming the most bandwidth over time. Unlike packet-level tools, NetFlow provides aggregated traffic statistics without storing full packet payloads, making it efficient for long-term WAN bandwidth monitoring.
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.
✓
NetFlow analyzer
Why this is correct
NetFlow collects flow records that show application-level details such as protocol and port numbers, enabling bandwidth usage analysis per application.
Related concept
Read the scenario before looking for a memorised answer.
✗
Packet sniffer (e.g., tcpdump)
Why it's wrong here
While a packet sniffer can capture full packets, it is heavy for long-term bandwidth analysis and does not aggregate data as effectively as NetFlow.
✗
Port scanner (e.g., Nmap)
Why it's wrong here
A port scanner identifies open ports on hosts but does not measure bandwidth consumption over time.
✗
Bandwidth speed test
Why it's wrong here
A speed test measures total throughput between two points, not application-level breakdown of bandwidth usage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between flow-based monitoring (NetFlow) and packet-level analysis (sniffers), trapping candidates who think a packet sniffer is the best tool for long-term bandwidth usage by application, when in fact it is too resource-intensive and lacks built-in aggregation for that purpose.
Detailed technical explanation
How to think about this question
NetFlow (version 5 or 9) exports flow records containing key fields like protocol number, source/destination port, and byte counts, which can be correlated with application protocols (e.g., TCP port 80 for HTTP, UDP 53 for DNS). In a real-world scenario, a NetFlow analyzer like SolarWinds or PRTG can generate top-N talkers reports, showing that, for example, HTTPS (TCP 443) consumes 60% of WAN bandwidth, while a packet sniffer would require manual filtering and aggregation to derive the same insight.
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 Operations — This question tests Network Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: NetFlow analyzer — A NetFlow analyzer is the correct tool because it collects flow-level metadata (e.g., source/destination IPs, ports, protocol, and byte counts) from routers or switches, enabling the administrator to identify which application protocols (via port/protocol analysis) are consuming the most bandwidth over time. Unlike packet-level tools, NetFlow provides aggregated traffic statistics without storing full packet payloads, making it efficient for long-term WAN bandwidth monitoring.
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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