- A
Attach an Internet Gateway to the private subnet and add a default route to the Internet Gateway in the private route table
Why wrong: This would allow inbound internet traffic to the private subnet.
- B
Assign an Elastic IP to the private instance and update the security group to allow outbound traffic
Why wrong: Assigning an EIP makes the instance publicly accessible.
- C
Add an Internet Gateway to the VPC and create a route in the private subnet to 0.0.0.0/0 via the Internet Gateway
Why wrong: Internet Gateway requires the subnet to be public; private subnet route table cannot route directly to IGW.
- D
Deploy a NAT Gateway in the public subnet and add a default route in the private subnet route table pointing to the NAT Gateway
NAT Gateway enables outbound-only internet access for private instances.
Quick Answer
The correct answer is to deploy a NAT Gateway in the public subnet and add a default route in the private subnet route table pointing to the NAT Gateway. This configuration works because the NAT Gateway, residing in a public subnet with an Internet Gateway, translates the private instance’s outbound traffic to its own Elastic IP, allowing the instance to reach the internet for patch downloads while the NAT Gateway drops any unsolicited inbound traffic. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how to architect secure outbound-only connectivity, often appearing in questions that contrast NAT Gateway, Internet Gateway, and proxy solutions. A common trap is assuming an Internet Gateway alone suffices for private instances, but it requires a route to a NAT device to function. Remember the mnemonic: “Private outbound? NAT’s the route—public subnet, default route.”
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 a CIDR of 10.0.0.0/16. The VPC has a public subnet 10.0.1.0/24 and a private subnet 10.0.2.0/24. An EC2 instance in the private subnet needs to download patches from the internet. Which configuration is required to provide outbound internet access to the private instance while preventing inbound internet traffic?
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 the public subnet and add a default route in the private subnet route table pointing to the NAT Gateway
Option C is correct because a NAT Gateway in the public subnet with a route in the private subnet route table pointing to the NAT Gateway provides outbound internet access. Option A is wrong because an Internet Gateway attached to the private subnet would allow inbound traffic. Option B is wrong because an EIP on the private instance directly exposes it. Option D is wrong because an Internet Gateway alone does not provide outbound access without a route to it.
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.
- ✗
Attach an Internet Gateway to the private subnet and add a default route to the Internet Gateway in the private route table
Why it's wrong here
This would allow inbound internet traffic to the private subnet.
- ✗
Assign an Elastic IP to the private instance and update the security group to allow outbound traffic
Why it's wrong here
Assigning an EIP makes the instance publicly accessible.
- ✗
Add an Internet Gateway to the VPC and create a route in the private subnet to 0.0.0.0/0 via the Internet Gateway
Why it's wrong here
Internet Gateway requires the subnet to be public; private subnet route table cannot route directly to IGW.
- ✓
Deploy a NAT Gateway in the public subnet and add a default route in the private subnet route table pointing to the NAT Gateway
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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 the public subnet and add a default route in the private subnet route table pointing to the NAT Gateway — Option C is correct because a NAT Gateway in the public subnet with a route in the private subnet route table pointing to the NAT Gateway provides outbound internet access. Option A is wrong because an Internet Gateway attached to the private subnet would allow inbound traffic. Option B is wrong because an EIP on the private instance directly exposes it. Option D is wrong because an Internet Gateway alone does not provide outbound access without a route to it.
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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