This DOP-C02 practice question tests your understanding of security and compliance. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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. They launch an EC2 instance in a private subnet that needs to download patches from the internet. Which solution is MOST secure and scalable?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a NAT Gateway in a public subnet and update the private route table.
Option C is correct because a NATGateway allows instances in private subnets to initiate outbound traffic to the internet and receive responses, without allowing inbound traffic. Option A is wrong because a public subnet exposes the instance to inbound traffic. Option B is wrong because a proxy server is less scalable and requires management. Option D is wrong because a VPC endpoint is for AWS services, not general internet.
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.
✓
Create a NAT Gateway in a public subnet and update the private route table.
Launch a proxy server in a public subnet and route traffic through it.
Why it's wrong here
Works but is less scalable and requires management.
✗
Assign an Elastic IP to the instance in the private subnet.
Why it's wrong here
Private subnets cannot have direct internet access; Elastic IP is not routable.
✗
Use a VPC endpoint to the Amazon Linux repository.
Why it's wrong here
VPC endpoints are for AWS services, not arbitrary internet patches.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
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: Create a NAT Gateway in a public subnet and update the private route table. — Option C is correct because a NAT Gateway allows instances in private subnets to initiate outbound traffic to the internet and receive responses, without allowing inbound traffic. Option A is wrong because a public subnet exposes the instance to inbound traffic. Option B is wrong because a proxy server is less scalable and requires management. Option D is wrong because a VPC endpoint is for AWS services, not general internet.
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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