- A
Deploy a NAT instance in a private subnet and add a default route to the NAT instance in the private subnet's route table.
Why wrong: A NAT instance in a private subnet cannot reach the internet itself, so it cannot provide outbound connectivity.
- B
Deploy an Application Load Balancer (ALB) in a public subnet and route outbound traffic through the ALB.
Why wrong: ALBs are for load balancing inbound traffic, not for providing outbound internet access.
- C
Attach an Internet Gateway to the VPC and add a default route to the Internet Gateway in the public subnet's route table.
Why wrong: This would allow inbound traffic to the public subnet, violating the requirement that web servers not be directly accessible.
- D
Deploy a NAT Gateway in a public subnet and add a default route to the NAT Gateway in the private subnet's route table.
A NAT Gateway in a public subnet enables instances in private subnets to initiate outbound traffic to the internet while remaining inaccessible from the internet.
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. 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 is deploying a multi-tier web application in a VPC with public and private subnets. The web servers in the public subnets must be able to initiate outbound connections to the internet for software updates, but must not be directly accessible from the internet. Which configuration meets these requirements?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Deploy a NAT Gateway in a public subnet and add a default route to the NAT Gateway in the private subnet's route table.
Option D is correct because a NAT Gateway in a public subnet allows instances in private subnets to initiate outbound traffic to the internet while remaining unreachable from the internet. Option A is wrong because an Internet Gateway alone would allow inbound traffic. Option B is wrong because a NAT Instance in a private subnet cannot reach the internet. Option C is wrong because an ALB does not provide outbound internet access.
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.
- ✗
Deploy a NAT instance in a private subnet and add a default route to the NAT instance in the private subnet's route table.
Why it's wrong here
A NAT instance in a private subnet cannot reach the internet itself, so it cannot provide outbound connectivity.
- ✗
Deploy an Application Load Balancer (ALB) in a public subnet and route outbound traffic through the ALB.
Why it's wrong here
ALBs are for load balancing inbound traffic, not for providing outbound internet access.
- ✗
Attach an Internet Gateway to the VPC and add a default route to the Internet Gateway in the public subnet's route table.
Why it's wrong here
This would allow inbound traffic to the public subnet, violating the requirement that web servers not be directly accessible.
- ✓
Deploy a NAT Gateway in a public subnet and add a default route to the NAT Gateway in the private subnet's route table.
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.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Deploy a NAT Gateway in a public subnet and add a default route to the NAT Gateway in the private subnet's route table. — Option D is correct because a NAT Gateway in a public subnet allows instances in private subnets to initiate outbound traffic to the internet while remaining unreachable from the internet. Option A is wrong because an Internet Gateway alone would allow inbound traffic. Option B is wrong because a NAT Instance in a private subnet cannot reach the internet. Option C is wrong because an ALB does not provide outbound internet access.
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.
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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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