- A
CodeBuild does not support VPC connectivity.
Why wrong: CodeBuild does support VPC connectivity when configured with a VPC.
- B
The VPC subnet has a NAT gateway that routes traffic to the internet instead of the internal network.
Why wrong: A NAT gateway is used for internet access; if the internal network is on-premises, a VPN or Direct Connect is used. The NAT gateway would not interfere with internal routing if the route table is correct.
- C
The security group for the PyPI repository does not allow inbound traffic from the CodeBuild security group.
The repository's security group must have an inbound rule allowing HTTPS traffic from the security group associated with the CodeBuild project's ENI.
- D
The VPC subnet does not have a route to the internal network.
Why wrong: While routing is important, the most common issue is security group rules blocking inbound traffic. The route could be correct but the security group may still block.
Quick Answer
The answer is that the security group for the PyPI repository is not allowing inbound traffic from the CodeBuild security group. When troubleshooting a CodeBuild VPC connectivity timeout, the most common oversight is focusing only on the outbound rules of the build environment while neglecting the inbound rules on the target resource. Even though the CodeBuild project correctly allows outbound HTTPS to 0.0.0.0/0, the private PyPI repository’s security group must explicitly permit inbound HTTPS traffic from the CodeBuild security group ID; otherwise, the connection is silently dropped. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of security group stateful filtering versus network ACL stateless filtering—a frequent trap is assuming outbound rules alone guarantee connectivity. Remember, security groups are stateful: if you allow outbound traffic, the return traffic is automatically permitted, but the target’s inbound rule is still required to initiate the connection. Memory tip: “Outbound is half the story—inbound opens the door.”
DOP-C02 Security and Compliance Practice Question
This DOP-C02 practice question tests your understanding of security and compliance. 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 uses AWS CodeBuild to build and test code. The build process requires access to a private PyPI repository hosted on an internal network. The CodeBuild project is configured with a VPC. However, the build fails with a timeout error when trying to connect to the PyPI repository. The security group for the CodeBuild project allows outbound HTTPS to 0.0.0.0/0. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The security group for the PyPI repository does not allow inbound traffic from the CodeBuild security group.
The private PyPI repository is in the internal network, which is likely accessible via a VPC. However, if the repository's security group does not allow inbound traffic from the CodeBuild security group, the connection will be blocked. The CodeBuild project's outbound rules are correct, but the repository side needs to allow inbound. Option A is wrong because the subnet must have a route to the internal network, which is usually via a VPC peering or VPN. Option C is wrong because if the subnet has a NAT gateway, the traffic would go to the internet, not to the internal network. Option D is wrong because a VPC endpoint is for AWS services, not for on-premises resources.
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.
- ✗
CodeBuild does not support VPC connectivity.
Why it's wrong here
CodeBuild does support VPC connectivity when configured with a VPC.
- ✗
The VPC subnet has a NAT gateway that routes traffic to the internet instead of the internal network.
- ✓
The security group for the PyPI repository does not allow inbound traffic from the CodeBuild security group.
Why this is correct
The repository's security group must have an inbound rule allowing HTTPS traffic from the security group associated with the CodeBuild project's ENI.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
- ✗
The VPC subnet does not have a route to the internal network.
Why it's wrong here
While routing is important, the most common issue is security group rules blocking inbound traffic. The route could be correct but the security group may still block.
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 DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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Security and Compliance — study guide chapter
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
Security and Compliance — This question tests Security and Compliance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The security group for the PyPI repository does not allow inbound traffic from the CodeBuild security group. — The private PyPI repository is in the internal network, which is likely accessible via a VPC. However, if the repository's security group does not allow inbound traffic from the CodeBuild security group, the connection will be blocked. The CodeBuild project's outbound rules are correct, but the repository side needs to allow inbound. Option A is wrong because the subnet must have a route to the internal network, which is usually via a VPC peering or VPN. Option C is wrong because if the subnet has a NAT gateway, the traffic would go to the internet, not to the internal network. Option D is wrong because a VPC endpoint is for AWS services, not for on-premises resources.
What should I do if I get this DOP-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 DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
This DOP-C02 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 DOP-C02 exam.
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