This DOP-C02 practice question tests your understanding of sdlc automation. 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 DevOps engineer is creating an AWS CloudFormation template to deploy a stack that includes an Amazon EC2 instance. The instance needs to be launched in a specific subnet. How should the engineer reference the subnet ID in the template?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Define a parameter (Parameters) of type AWS::EC2::Subnet::Id and reference it.
Option C is correct because using a parameter allows the subnet ID to be passed in at stack creation time, making the template reusable. Option A is wrong because hardcoding reduces reusability. Option B is wrong because mappings are for static values, not dynamic IDs. Option D is wrong because the Fn::GetAtt function is used to get attributes of resources created in the same stack, not for parameters.
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.
✗
Hardcode the subnet ID in the template.
Why it's wrong here
Hardcoding makes the template non-reusable across different environments.
✗
Use a mapping (Mappings) to define the subnet ID based on the stack name.
Why it's wrong here
Mappings are for static key-value pairs; subnet IDs are not predictable.
✓
Define a parameter (Parameters) of type AWS::EC2::Subnet::Id and reference it.
Why this is correct
Parameters allow the user to specify the subnet ID at stack creation.
Use the Fn::GetAtt function to retrieve the subnet ID from a VPC resource.
Why it's wrong here
Fn::GetAtt returns attributes of a resource, but the subnet is not created in the stack.
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.
SDLC Automation — This question tests SDLC Automation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Define a parameter (Parameters) of type AWS::EC2::Subnet::Id and reference it. — Option C is correct because using a parameter allows the subnet ID to be passed in at stack creation time, making the template reusable. Option A is wrong because hardcoding reduces reusability. Option B is wrong because mappings are for static values, not dynamic IDs. Option D is wrong because the Fn::GetAtt function is used to get attributes of resources created in the same stack, not for parameters.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.