The answer is to use network security groups (NSGs) on each subnet. This is correct because NSGs act as a stateful, built-in firewall that filters traffic at the subnet or NIC level, allowing you to define granular inbound and outbound security rules. By applying an NSG to the web tier subnet with an inbound rule allowing internet traffic on ports 80/443, and separate NSGs on the application and database subnets with rules that only permit traffic from the preceding tier’s subnet, you effectively isolate the multi-tier application NSG architecture without additional cost or complexity. On the AZ-500 exam, this scenario tests your understanding of network segmentation and least-privilege access—a common trap is choosing Azure Firewall for simple tier isolation, which is overkill and not cost-effective, or VNet peering, which connects networks but does not filter traffic. A useful memory tip: think of NSGs as “subnet bouncers” that only let in traffic from the tier directly above, keeping your database tier completely hidden from the internet.
AZ-500 Secure networking Practice Question
This AZ-500 practice question tests your understanding of secure networking. 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 manage a multi-tier application in Azure with a web tier, application tier, and database tier. The web tier must be accessible from the internet, but the application and database tiers must only be accessible from the web tier. Which Azure networking feature should you use to isolate the tiers?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Network security groups (NSGs) on each subnet.
Option A is correct because network security groups (NSGs) can be applied to subnets to control inbound and outbound traffic between tiers. The other options either don't provide isolation (VNet peering) or are not cost-effective (Azure Firewall for simple rules).
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.
✗
Virtual network peering between tiers.
Why it's wrong here
VNet peering connects networks but does not isolate; it would allow all traffic unless combined with NSGs.
✗
Azure Firewall with application rules.
Why it's wrong here
Azure Firewall can be used but is an additional cost and more complex than NSGs for simple isolation.
✓
Network security groups (NSGs) on each subnet.
Why this is correct
NSGs allow you to define rules to permit or deny traffic between subnets, effectively isolating tiers.
Application security groups (ASGs) within the same subnet.
Why it's wrong here
ASGs group VMs but do not inherently isolate traffic; they are used with NSG rules, not alone.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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 networking — This question tests Secure networking — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Network security groups (NSGs) on each subnet. — Option A is correct because network security groups (NSGs) can be applied to subnets to control inbound and outbound traffic between tiers. The other options either don't provide isolation (VNet peering) or are not cost-effective (Azure Firewall for simple rules).
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.
About these practice questions
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Variation 1. You are designing a secure network architecture for a three-tier application. The web tier must be accessible from the internet, while the application and database tiers must only be accessible from the web tier. Which Azure service should you use to isolate the tiers most securely?
easy
A.Azure Firewall with application rules
B.Azure Front Door with Web Application Firewall
✓ C.Network security groups (NSGs) on subnets
D.VNet peering between tiers
Why C: Option A is correct because NSGs with subnet-level rules can restrict traffic between tiers. Option B is wrong because Azure Firewall is a centralized firewall, but for simple tier isolation, NSGs are more appropriate and cost-effective. Option C is wrong because VNet peering connects networks, not isolates tiers. Option D is wrong because Azure Front Door is for global load balancing, not tier isolation.
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Question Discussion
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