Quick Answer
The answer is VPC Flow Logs. This AWS service captures IP traffic information for network interfaces within a VPC, allowing you to monitor all network traffic entering and leaving your subnets for security analysis and troubleshooting. Unlike CloudTrail, which logs API calls, or Config, which records resource configuration changes, VPC Flow Logs provide granular visibility into the actual data packets flowing across your network. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your ability to distinguish between logging, monitoring, and threat detection services—a common trap is confusing GuardDuty, which consumes flow logs for threat detection, with the service that captures the traffic itself. Remember: if you need to see the raw network traffic metadata, think Flow Logs; for API activity, think CloudTrail. A simple mnemonic is “Flows for flows, Trails for tails”—where “tails” refers to the trail of API calls.
This ANS-C01 practice question tests your understanding of network implementation. 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 has a VPC with multiple subnets. They want to monitor all network traffic entering and leaving the VPC for security analysis. Which AWS service should they use?
AWS CloudTrail
Why wrong: CloudTrail logs API activity, not network traffic.
AWS Config
Why wrong: Config monitors resource configurations.
Amazon GuardDuty
Why wrong: GuardDuty is a threat detection service that uses flow logs but does not capture them.
VPC Flow Logs
VPC Flow Logs capture network traffic metadata.
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
Option D is correct. VPC Flow Logs capture IP traffic information. Option A is wrong because CloudTrail logs API calls. Option B is wrong because Config records resource changes. Option C is wrong because GuardDuty is a threat detection service that uses flow logs but does not capture traffic itself.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
AWS Config
Why it's wrong here
Config monitors resource configurations.
Amazon GuardDuty
Why it's wrong here
GuardDuty is a threat detection service that uses flow logs but does not capture them.
VPC Flow Logs
Why this is correct
VPC Flow Logs capture network traffic metadata.
Related concept
CIDR notation defines the prefix length.
Common exam traps
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
The correct answer is: VPC Flow Logs — Option D is correct. VPC Flow Logs capture IP traffic information. Option A is wrong because CloudTrail logs API calls. Option B is wrong because Config records resource changes. Option C is wrong because GuardDuty is a threat detection service that uses flow logs but does not capture traffic itself.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 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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