The answer is to attach a NAT gateway to the private subnet's route table. This is correct because a NAT gateway enables instances in a private subnet to initiate outbound internet traffic for tasks like downloading dependencies, while preventing inbound traffic from the internet. Without a NAT gateway, a private subnet has no route to the internet, causing CodeBuild build failures with timeout errors when it tries to reach external repositories. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of VPC networking and how to troubleshoot CodeBuild failures in isolated environments. A common trap is confusing VPC endpoints (which only work for AWS services like S3) with the need for general internet access, or assuming a public subnet is required when the question specifies a private subnet. Remember the key distinction: for private subnets needing internet access, think NAT gateway, not endpoints or proxies. Memory tip: “Private needs NAT to chat with the outside world.”
SOA-C02 Deployment, Provisioning, and Automation Practice Question
This SOA-C02 practice question tests your understanding of deployment, provisioning, and automation. 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 SysOps administrator is troubleshooting a failed AWS CodeBuild build. The build project uses an Amazon S3 source. The buildspec.yml file includes commands that require internet access to download dependencies. The build is failing with a timeout error when trying to download from an external repository. The VPC configuration for the build project uses a private subnet with no NAT gateway. What change should be made to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Attach a NAT gateway to the private subnet's route table.
Option B is correct because a NATgateway or NAT instance is required to allow instances in a private subnet to access the internet. Option A is incorrect because a public subnet would provide internet access directly, but the question implies the build must be in a private subnet. Option C is incorrect because VPC endpoints are for accessing AWS services, not the internet. Option D is incorrect because a proxy is not the standard solution; NAT is.
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 a NAT gateway to the private subnet's route table.
Why this is correct
NATgateway allows outbound internet access from private subnet.
A proxy would still need outbound internet access via NAT.
✗
Create a VPC endpoint for the external repository.
Why it's wrong here
VPC endpoints are for AWS services, not external repositories.
✗
Move the build project to a public subnet with an internet gateway.
Why it's wrong here
This would work but may not be desired if the build must be in a private subnet.
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 SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Deployment, Provisioning, and Automation — This question tests Deployment, Provisioning, and Automation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Attach a NAT gateway to the private subnet's route table. — Option B is correct because a NAT gateway or NAT instance is required to allow instances in a private subnet to access the internet. Option A is incorrect because a public subnet would provide internet access directly, but the question implies the build must be in a private subnet. Option C is incorrect because VPC endpoints are for accessing AWS services, not the internet. Option D is incorrect because a proxy is not the standard solution; NAT is.
What should I do if I get this SOA-C02 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 SOA-C02 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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Question Discussion
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