Quick Answer
The answer is VPC Flow Logs, the correct AWS service for capturing and analyzing network traffic between EC2 instances within the same VPC. This service works by capturing IP traffic metadata—such as source and destination IP addresses, ports, protocol, and packet and byte counts—at the VPC, subnet, or network interface level, providing the granular network-level visibility needed to troubleshoot traffic flows without requiring any agents or changes to the instances. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding of native monitoring tools versus agent-based solutions; a common trap is to confuse VPC Flow Logs with AWS CloudTrail or AWS Config, which log API calls and resource changes, not network traffic. Remember that VPC Flow Logs capture metadata only, not packet payloads, so they are ideal for analyzing traffic patterns but not for deep packet inspection. A helpful memory tip is to think of Flow Logs as the “who, what, and where” of network conversations—source, destination, and protocol—without the “what was said.”
This ANS-C01 practice question tests your understanding of network design. 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 company has a VPC with multiple subnets. They want to capture and analyze network traffic between EC2 instances in the same VPC for troubleshooting. Which AWS service should be used?
VPC Flow Logs
Captures network traffic metadata for analysis.
AWS CloudTrail
Why wrong: Captures API activity, not network traffic.
AWS Config
Why wrong: Tracks resource configuration changes.
Amazon CloudWatch Metrics
Why wrong: Monitors performance metrics, not network packets.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VPC Flow Logs
VPC Flow Logs capture IP traffic metadata (source/destination IP, ports, protocol, packet/byte counts) at the VPC, subnet, or network interface level, enabling detailed analysis of traffic between EC2 instances within the same VPC. This is the correct service because it provides the network-level visibility needed for troubleshooting traffic flows without requiring agents or changes to the instances.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
VPC Flow Logs
Why this is correct
Captures network traffic metadata for analysis.
Related concept
Read the scenario before looking for a memorised answer.
AWS CloudTrail
Why it's wrong here
Captures API activity, not network traffic.
AWS Config
Why it's wrong here
Tracks resource configuration changes.
Amazon CloudWatch Metrics
Why it's wrong here
Monitors performance metrics, not network packets.
Common exam traps
The trap here is that candidates confuse VPC Flow Logs with CloudTrail, thinking CloudTrail captures network traffic because it logs 'events,' but CloudTrail only logs AWS API calls, not the data-plane traffic between instances.
Detailed technical explanation
VPC Flow Logs publish flow records to Amazon CloudWatch Logs or Amazon S3, capturing fields like srcaddr, dstaddr, srcport, dstport, protocol (IANA protocol numbers), and action (ACCEPT/REJECT). A subtle behavior is that flow logs are aggregated and published every 10 minutes by default (or 1 minute with the enhanced 1-minute aggregation), and they do not capture the actual payload of packets—only metadata—so they cannot be used for deep packet inspection or content analysis.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
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FAQ
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
The correct answer is: VPC Flow Logs — VPC Flow Logs capture IP traffic metadata (source/destination IP, ports, protocol, packet/byte counts) at the VPC, subnet, or network interface level, enabling detailed analysis of traffic between EC2 instances within the same VPC. This is the correct service because it provides the network-level visibility needed for troubleshooting traffic flows without requiring agents or changes to the instances.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.
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