The correct actions are to place web servers in a public subnet with an Internet Gateway and to place application and database servers in private subnets. This design works because a public subnet has a route to an Internet Gateway, allowing inbound traffic from the internet to reach the web tier, while private subnets lack that direct route, isolating the sensitive tiers from external access. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of subnet routing and the distinction between public and private subnet architecture, a foundational concept for multi-tier web applications. A common trap is confusing a NAT Gateway, which only provides outbound internet access, with an Internet Gateway for inbound traffic. Remember the memory tip: "Public for inbound, private for isolation, and never use a NAT for a front door."
ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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's security team is designing a network architecture for a multi-tier application. The web tier must be accessible from the internet, while the application and database tiers must be isolated. Which TWO actions should be taken to meet these requirements?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Place application and database servers in private subnets
Options A and D are correct. Public subnets for the web tier allow internet access via an Internet Gateway. Private subnets for app and database tiers isolate them. Option B is wrong because NAT gateway is for outbound internet access, not inbound. Option C is wrong because VPC endpoints are for AWS services, not internet. Option E is wrong because security groups alone do not provide subnet 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.
✗
Place application and database servers in a public subnet with a VPC endpoint
Why it's wrong here
Public subnet would expose them to internet; VPC endpoints are not for internet access.
✗
Place web servers in a private subnet with a NAT Gateway
Why it's wrong here
Private subnet with NAT does not allow inbound internet traffic.
✓
Place application and database servers in private subnets
Why this is correct
Private subnets isolate them from direct internet access.
Use security group rules to allow traffic only between tiers
Why it's wrong here
Security groups control traffic but do not provide subnet-level isolation; they are complementary.
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 Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Place application and database servers in private subnets — Options A and D are correct. Public subnets for the web tier allow internet access via an Internet Gateway. Private subnets for app and database tiers isolate them. Option B is wrong because NAT gateway is for outbound internet access, not inbound. Option C is wrong because VPC endpoints are for AWS services, not internet. Option E is wrong because security groups alone do not provide subnet isolation.
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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