- A
Two subnets: public for web, private for app and database together
Why wrong: App and database would not be isolated from each other.
- B
Three subnets: public for web, private for app, and private for database with stricter security groups
This provides proper isolation: web in public, app in private, database in isolated private subnet.
- C
One public subnet for all tiers
Why wrong: This would expose all tiers to the internet, violating security.
- D
Four subnets: two public for redundancy, two private for app and database
Why wrong: Redundant public subnets are common, but four subnets are not necessary for the isolation requirement; three is sufficient.
Question 678 of 997
CV0-004 Cloud Architecture and Design Practice Question
This CV0-004 practice question tests your understanding of cloud architecture and design. 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 cloud engineer is designing a VPC in AWS for a three-tier web application. The web servers must be accessible from the internet, the application servers must be isolated from the internet but reachable by web servers, and the database servers must be isolated from both. How many subnets should be created, and which type should each be?
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
✓
Three subnets: public for web, private for app, and private for database with stricter security groups
A three-tier architecture typically uses three subnets: public for web servers, private for application servers, and a database subnet (often private with additional restrictions). The database subnet is typically private, but the question asks for isolation, implying a separate subnet tier. A single subnet cannot provide isolation. Two subnets would combine two tiers, violating isolation.
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.
- ✗
Two subnets: public for web, private for app and database together
Why it's wrong here
App and database would not be isolated from each other.
- ✓
Three subnets: public for web, private for app, and private for database with stricter security groups
Why this is correct
This provides proper isolation: web in public, app in private, database in isolated private subnet.
Related concept
CIDR notation defines the prefix length.
- ✗
One public subnet for all tiers
Why it's wrong here
This would expose all tiers to the internet, violating security.
- ✗
Four subnets: two public for redundancy, two private for app and database
Why it's wrong here
Redundant public subnets are common, but four subnets are not necessary for the isolation requirement; three is sufficient.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Visual reference
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 CV0-004 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this CV0-004 question test?
Cloud Architecture and Design — This question tests Cloud Architecture and Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Three subnets: public for web, private for app, and private for database with stricter security groups — A three-tier architecture typically uses three subnets: public for web servers, private for application servers, and a database subnet (often private with additional restrictions). The database subnet is typically private, but the question asks for isolation, implying a separate subnet tier. A single subnet cannot provide isolation. Two subnets would combine two tiers, violating isolation.
What should I do if I get this CV0-004 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 CV0-004 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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Last reviewed: Jul 4, 2026
This CV0-004 practice question is part of Courseiva's free CompTIA 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 CV0-004 exam.
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