The answer is to use separate subnets for each tier in the same VNet and configure NSGs to allow traffic only from the previous tier. This approach is the most secure and manageable because it leverages network segmentation for multi-tier VMs using subnets and NSGs, creating logical isolation between the web, application, and database layers while maintaining a flat network topology within a single VNet. By applying NSG rules that restrict inbound traffic to the database subnet solely from the application subnet, and the application subnet solely from the web subnet, you enforce a strict east-west traffic flow that minimizes the attack surface. On the Microsoft Azure Security Engineer Associate AZ-500 exam, this scenario tests your understanding of defense-in-depth and the principle of least privilege at the network layer; a common trap is to overcomplicate the solution with Azure Firewall or VNet peering when simple subnetting and NSGs suffice. Remember the memory tip: "Three tiers, three subnets, one VNet, NSGs gate the way—peerless and firewall-free."
AZ-500 Secure compute, storage, and databases Practice Question
This AZ-500 practice question tests your understanding of secure compute, storage, and databases. 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.
You are deploying a three-tier application on Azure VMs. The web tier must be accessible from the internet, but the application and database tiers must only accept traffic from the web tier. You need to implement network segmentation using Azure networking components. What is the most secure and manageable solution?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use separate subnets for each tier in the same VNet and configure NSGs to allow traffic only from the previous tier.
Option B is correct because placing each tier in separate subnets with NSGs restricting traffic to the previous tier provides network segmentation and is manageable. Option A is wrong because VNet peering connects separate VNets but doesn't provide fine-grained control within a single VNet. Option C is wrong because a single subnet with NSGs is less secure due to lack of isolation. Option D is wrong because Azure Firewall is more expensive and complex than NSGs for this scenario.
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 a single subnet and configure NSGs on VM NICs to restrict traffic.
Why it's wrong here
Single subnet does not isolate tiers; NIC NSGs are per-VM and harder to manage.
✗
Use VNet peering to connect separate VNets for each tier and use NSGs.
Why it's wrong here
VNet peering is for connecting different VNets, not required for tiers within same VNet, adds complexity.
✗
Use a single VNet with one subnet and use Azure Firewall to filter traffic between tiers.
Why it's wrong here
A single subnet lacks isolation; Azure Firewall is overkill and more expensive.
✓
Use separate subnets for each tier in the same VNet and configure NSGs to allow traffic only from the previous tier.
Why this is correct
Separate subnets provide isolation; NSGs enforce least-privilege network 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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-500 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related AZ-500 subnetting questions on CIDR, address ranges, and subnet selection.
Secure compute, storage, and databases — This question tests Secure compute, storage, and databases — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Use separate subnets for each tier in the same VNet and configure NSGs to allow traffic only from the previous tier. — Option B is correct because placing each tier in separate subnets with NSGs restricting traffic to the previous tier provides network segmentation and is manageable. Option A is wrong because VNet peering connects separate VNets but doesn't provide fine-grained control within a single VNet. Option C is wrong because a single subnet with NSGs is less secure due to lack of isolation. Option D is wrong because Azure Firewall is more expensive and complex than NSGs for this scenario.
What should I do if I get this AZ-500 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 AZ-500 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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