The answer is to enable VPC Flow Logs specifically on the NAT gateway’s elastic network interface. This is correct because VPC Flow Logs capture traffic at the network interface level, not at the subnet or VPC level; the NAT gateway has its own ENI in the public subnet, and outbound traffic from private instances is encapsulated and forwarded through that interface, so flow logs on the private subnet ENIs only show internal VPC traffic. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding that NAT gateway traffic is not logged by default—you must explicitly target the gateway’s ENI, a common trap where candidates mistakenly enable flow logs on the private subnet instead. A key memory tip is “follow the packet”: to log outbound internet traffic, you must log the interface that actually sends the packet to the internet, which is the NAT gateway’s ENI, not the source instance’s ENI.
ANS-C01 Network Management and Operations Practice Question
This ANS-C01 practice question tests your understanding of network management and operations. 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 public and private subnets. The public subnets have a NAT gateway for outbound internet access. The private subnets route all 0.0.0.0/0 traffic to the NAT gateway. The network team wants to centrally log all outbound internet traffic from the private subnets. They enable VPC Flow Logs and publish them to Amazon S3. However, they notice that the flow logs are capturing only traffic between instances within the VPC, not the NAT gateway traffic. What should the team do to capture outbound internet traffic?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable VPC Flow Logs specifically for the NAT gateway's elastic network interface.
VPC Flow Logs capture traffic at the network interface level. To capture traffic that goes through the NATgateway, you need to enable flow logs on the NAT gateway's network interface. Option B is the correct approach. Option A is not necessary because NAT gateway traffic is not VPC-to-VPC. Option C would capture traffic but not specifically the outbound traffic. Option D is incorrect because the issue is not with VPC Flow Logs configuration but with the resource being monitored.
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Enable VPC Flow Logs specifically for the NAT gateway's elastic network interface.
Enable VPC Flow Logs for the VPC and publish to CloudWatch Logs instead of S3.
Why it's wrong here
Does not change what traffic is captured.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
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
How to think about this question
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.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
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
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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.
Network Management and Operations — This question tests Network Management and Operations — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Enable VPC Flow Logs specifically for the NAT gateway's elastic network interface. — VPC Flow Logs capture traffic at the network interface level. To capture traffic that goes through the NAT gateway, you need to enable flow logs on the NAT gateway's network interface. Option B is the correct approach. Option A is not necessary because NAT gateway traffic is not VPC-to-VPC. Option C would capture traffic but not specifically the outbound traffic. Option D is incorrect because the issue is not with VPC Flow Logs configuration but with the resource being monitored.
What should I do if I get this ANS-C01 question wrong?
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has a VPC with public and private subnets. The private subnets have a route to a NAT gateway for outbound internet access. The security team wants to audit all traffic from the private subnets to the internet. Which TWO steps should be taken to capture this traffic?
medium
A.Enable VPC Flow Logs on the internet gateway.
✓ B.Create a VPC Flow Log for the VPC and filter by the NAT gateway's network interface.
✓ C.Enable VPC Flow Logs on the NAT gateway's elastic network interface.
D.Set up an AWS Site-to-Site VPN to route traffic through a third-party logging appliance.
E.Enable AWS CloudTrail for the NAT gateway.
Why B: Option A is correct because VPC Flow Logs capture traffic for the NAT gateway interface. Option D is correct because enabling flow logs on the NAT gateway captures traffic sent through it. Option B is incorrect because the internet gateway does not see traffic from private subnets. Option C is incorrect because CloudTrail does not capture network traffic. Option E is incorrect because VPN is not used here.
Last reviewed: Jun 20, 2026
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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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