The answer is nested stacks, because they enable you to encapsulate and reuse a common CloudFormation template—such as one defining a VPC and subnets—by referencing it from multiple parent stacks. This promotes modularity and avoids duplicating resource definitions across environments. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this question tests your understanding of template reuse patterns versus other features like cross-stack references (which only pass output values, not definitions) or StackSets (which deploy identical stacks across accounts or regions). A common trap is confusing nested stacks with cross-stack references: remember that nested stacks reuse the *template itself*, while cross-stack references reuse only *output values* from another stack. For a quick memory tip, think “nest the template, cross the value.”
DOP-C02 SDLC Automation Practice Question
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 team uses AWS CloudFormation to manage infrastructure. They want to reuse a common set of resources (e.g., VPC, subnets) across multiple stacks. Which CloudFormation feature should they use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Nested stacks
Option A is correct because nested stacks allow reusing a common template. Option B is wrong because cross-stack references allow passing values but not reusing resource definitions. Option C is wrong because custom resources are for extending CloudFormation. Option D is wrong because StackSets deploy across accounts/regions.
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.
✗
Custom resources
Why it's wrong here
Custom resources are for provisioning resources not natively supported.
✗
StackSets
Why it's wrong here
StackSets are for deploying stacks across multiple accounts/regions, not for reuse within a single account.
✗
Cross-stack references
Why it's wrong here
Cross-stack references allow passing outputs between stacks but not reusing resource definitions.
✓
Nested stacks
Why this is correct
Nested stacks allow a template to reference another template, enabling reuse.
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.
Trap categories for this question
Command / output trap
Cross-stack references allow passing outputs between stacks but not reusing resource definitions.
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: Nested stacks — Option A is correct because nested stacks allow reusing a common template. Option B is wrong because cross-stack references allow passing values but not reusing resource definitions. Option C is wrong because custom resources are for extending CloudFormation. Option D is wrong because StackSets deploy across accounts/regions.
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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