Quick Answer
The answer is VPC Flow Logs. This AWS service is the correct choice for monitoring network traffic to and from EC2 instances because it captures IP traffic metadata—including source and destination IPs, ports, protocols, and whether packets were accepted or rejected—at the network interface level, all without requiring any agent installation on the instances. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding of native, agentless logging versus agent-based solutions like the CloudWatch agent or third-party tools; a common trap is confusing VPC Flow Logs with AWS CloudTrail, which records API calls, not network traffic. Remember that Flow Logs log the flow, not the action—they show packet-level metadata, not application payloads. A useful memory tip: think of VPC Flow Logs as the network’s black box recorder, capturing who talked to whom, on which port, and whether the conversation was allowed or denied.
This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 needs to monitor network traffic to and from EC2 instances for security analysis. Which AWS service should they use?
AWS CloudTrail
Why wrong: CloudTrail logs API activity, not network traffic.
Amazon CloudWatch Logs
Why wrong: CloudWatch Logs can store logs but does not capture network traffic.
AWS Config
Why wrong: AWS Config tracks configuration changes, not traffic.
VPC Flow Logs
VPC Flow Logs capture IP traffic information.
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 information for network interfaces in a VPC, including metadata such as source/destination IPs, ports, protocols, and packet accept/reject decisions. This makes it the correct service for monitoring network traffic to and from EC2 instances for security analysis, as it provides detailed network-level logs without requiring any agent installation on 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.
AWS CloudTrail
Why it's wrong here
CloudTrail logs API activity, not network traffic.
Amazon CloudWatch Logs
Why it's wrong here
CloudWatch Logs can store logs but does not capture network traffic.
AWS Config
Why it's wrong here
AWS Config tracks configuration changes, not traffic.
VPC Flow Logs
Why this is correct
VPC Flow Logs capture IP traffic information.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse AWS CloudTrail (API auditing) with network traffic monitoring, or assume CloudWatch Logs can capture network flows directly, but VPC Flow Logs are the only service that provides raw network traffic metadata at the VPC level.
Detailed technical explanation
VPC Flow Logs publish flow log records to Amazon CloudWatch Logs or Amazon S3, capturing fields like srcaddr, dstaddr, srcport, dstport, protocol, and action (ACCEPT/REJECT) based on the 5-tuple of the traffic. A subtle behavior is that flow logs are aggregated and published every 10 minutes by default (or 1 minute with a higher aggregation interval), and they do not capture traffic generated by AWS services like Amazon DNS or Amazon DHCP unless specifically configured. In a real-world scenario, a security analyst might use VPC Flow Logs to detect anomalous outbound connections to known malicious IPs, which CloudTrail or Config could not reveal.
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 information for network interfaces in a VPC, including metadata such as source/destination IPs, ports, protocols, and packet accept/reject decisions. This makes it the correct service for monitoring network traffic to and from EC2 instances for security analysis, as it provides detailed network-level logs without requiring any agent installation on 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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