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 need to block inbound traffic from the internet to a specific subnet except for TCP port 443. Which Azure service should you use?
Azure Web Application Firewall (WAF)
Why wrong: WAF protects web applications, not general subnet traffic.
Azure Firewall
Why wrong: Azure Firewall can also do this, but NSGs are simpler and free for basic filtering.
Network security group (NSG)
NSGs can filter inbound traffic based on port and source.
Azure DDoS Protection
Why wrong: DDoS Protection mitigates volumetric attacks, not port-based filtering.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Network security group (NSG)
Option A is correct because NSGs can have inbound rules to allow or deny traffic by port. Option B is wrong because Azure Firewall is a network/application firewall but NSGs are simpler for subnet-level filtering. Option C is wrong because WAF is for HTTP/HTTPS at the application layer. Option D is wrong because DDoS Protection does not filter by port.
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
For each option: why learners choose it and why it is or isn't the right answer here.
Azure Web Application Firewall (WAF)
Why it's wrong here
WAF protects web applications, not general subnet traffic.
Azure Firewall
Why it's wrong here
Azure Firewall can also do this, but NSGs are simpler and free for basic filtering.
Network security group (NSG)
Why this is correct
NSGs can filter inbound traffic based on port and source.
Related concept
CIDR notation defines the prefix length.
Azure DDoS Protection
Why it's wrong here
DDoS Protection mitigates volumetric attacks, not port-based filtering.
Common exam traps
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
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.
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
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
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.
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FAQ
Secure networking — This question tests Secure networking — CIDR notation defines the prefix length..
The correct answer is: Network security group (NSG) — Option A is correct because NSGs can have inbound rules to allow or deny traffic by port. Option B is wrong because Azure Firewall is a network/application firewall but NSGs are simpler for subnet-level filtering. Option C is wrong because WAF is for HTTP/HTTPS at the application layer. Option D is wrong because DDoS Protection does not filter by port.
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.
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
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