Quick Answer
The correct answer is NAT gateway, VPC Flow Logs, and Amazon GuardDuty. This combination works because the NAT gateway routes all outbound traffic from private subnets to the internet, VPC Flow Logs capture metadata about every connection, and GuardDuty analyzes those flow logs to detect malicious activity like port scanning or data exfiltration. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this tests your understanding of how to layer detective controls on egress traffic without introducing inline inspection overhead. A common trap is selecting Network Firewall or Internet Gateway—Network Firewall can inspect but is not required for this specific pattern, and Internet Gateway handles inbound traffic, not outbound. Remember the mnemonic: NAT routes, Logs record, GuardDuty detects—the three-step outbound inspection chain.
This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 public and private subnets. The security team wants to inspect all traffic leaving the VPC to the internet for malicious activity. Which THREE services should be used together to achieve this? (Choose three.)
VPC Flow Logs
Captures network traffic metadata for analysis.
Internet gateway
Why wrong: Internet gateway is for inbound/outbound but not required for private subnets outbound.
Amazon GuardDuty
Analyzes flow logs for threats.
AWS Network Firewall
Why wrong: Can also inspect, but the question asks for three and this is not needed with GuardDuty.
NAT gateway
Routes outbound traffic from private subnets.
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
A NAT gateway routes outbound traffic, VPC Flow Logs capture metadata, and Amazon GuardDuty analyzes flow logs for threats. Options A, C, and D are correct. Option B is wrong because Internet Gateway is for inbound. Option E is wrong because Network Firewall can inspect, but the combination of NAT, Flow Logs, and GuardDuty is a common pattern for outbound inspection.
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.
VPC Flow Logs
Why this is correct
Captures network traffic metadata for analysis.
Related concept
CIDR notation defines the prefix length.
Internet gateway
Why it's wrong here
Internet gateway is for inbound/outbound but not required for private subnets outbound.
Amazon GuardDuty
Why this is correct
Analyzes flow logs for threats.
Related concept
CIDR notation defines the prefix length.
AWS Network Firewall
Why it's wrong here
Can also inspect, but the question asks for three and this is not needed with GuardDuty.
NAT gateway
Why this is correct
Routes outbound traffic from private subnets.
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 Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
The correct answer is: VPC Flow Logs — A NAT gateway routes outbound traffic, VPC Flow Logs capture metadata, and Amazon GuardDuty analyzes flow logs for threats. Options A, C, and D are correct. Option B is wrong because Internet Gateway is for inbound. Option E is wrong because Network Firewall can inspect, but the combination of NAT, Flow Logs, and GuardDuty is a common pattern for outbound inspection.
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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