This ANS-C01 practice question tests your understanding of network implementation. 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 is running a two-tier application with a web tier and a database tier. The web tier must be accessible from the internet, but the database tier should only be accessible from the web tier. Which architecture 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
✓
Web tier in public subnet, database tier in private subnet with a security group allowing only web tier.
The correct answer is C because placing the web tier in a public subnet with an Internet Gateway and the database tier in a private subnet with a security group that allows traffic only from the web tier provides the required security. Option A (both in public) exposes the database. Option B (both in private) prevents internet access. Option D (database in public) is insecure.
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.
✓
Web tier in public subnet, database tier in private subnet with a security group allowing only web tier.
Why this is correct
This architecture provides internet access to the web tier and isolates the database.
Both tiers in public subnets with security groups restricting database access.
Why it's wrong here
Placing the database in a public subnet exposes it unnecessarily.
✗
Both tiers in private subnets with a NAT Gateway for internet access.
Why it's wrong here
A NATGateway would not allow inbound internet traffic to the web tier.
✗
Web tier in private subnet, database tier in public subnet with a security group.
Why it's wrong here
This exposes the database to the internet.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Web tier in public subnet, database tier in private subnet with a security group allowing only web tier. — The correct answer is C because placing the web tier in a public subnet with an Internet Gateway and the database tier in a private subnet with a security group that allows traffic only from the web tier provides the required security. Option A (both in public) exposes the database. Option B (both in private) prevents internet access. Option D (database in public) is insecure.
What should I do if I get this ANS-C01 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 ANS-C01 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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