This CV0-004 practice question tests your understanding of operations and support. 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 cloud engineer is tasked with automating the deployment of a three-tier application. The engineer wants to ensure that the database tier is not directly accessible from the internet but can be reached by the application tier. Which of the following should be implemented?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Place the database tier in a private subnet and configure a security group to allow traffic only from the application tier
Option C is correct: placing the database tier in a private subnet with a network security group allowing only the app tier. Option A is wrong: public subnet would expose the database. Option B is wrong: a single subnet could still have NSGs but doesn't enforce isolation. Option D is wrong: a VPN for database access is overkill and introduces latency.
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.
✗
Use the same subnet for all tiers and allow traffic via security groups
Why it's wrong here
Does not isolate the database tier from potential compromise.
✗
Place the database tier in a public subnet with a restrictive security group
Why it's wrong here
Public subnet is reachable from internet, even with restrictive rules.
✗
Connect the database tier to a site-to-site VPN and disable public access
Why it's wrong here
Unnecessary complexity; can be done within VPC.
✓
Place the database tier in a private subnet and configure a security group to allow traffic only from the application tier
Why this is correct
Private subnet has no internet gateway, and security group restricts access.
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.
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.
Operations and Support — This question tests Operations and Support — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Place the database tier in a private subnet and configure a security group to allow traffic only from the application tier — Option C is correct: placing the database tier in a private subnet with a network security group allowing only the app tier. Option A is wrong: public subnet would expose the database. Option B is wrong: a single subnet could still have NSGs but doesn't enforce isolation. Option D is wrong: a VPN for database access is overkill and introduces latency.
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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Question Discussion
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