The answer is Network Security Groups (NSGs). NSGs are the correct choice because they provide stateful, layer-3/4 traffic filtering at the subnet or NIC level, allowing you to enforce NSG subnet isolation for frontend backend SQL Azure communication. By applying an NSG to the Backend subnet with a deny-all rule for internet traffic and a higher-priority allow rule for inbound traffic from the Frontend subnet on TCP port 1433, you achieve the required isolation while permitting necessary SQL access. On the Microsoft Azure Security Engineer Associate AZ-500 exam, this scenario tests your understanding of network segmentation and least-privilege access; a common trap is confusing NSGs with Azure Firewall or Service Endpoints, but NSGs are the lightweight, subnet-level solution for this specific need. Memory tip: think "NSG for subnet segregation, Firewall for perimeter inspection"—when the question focuses on subnet-to-subnet rules and blocking internet ingress at the subnet boundary, NSGs are your go-to.
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.
A virtual network has a Frontend subnet (web servers) and a Backend subnet (Azure SQL Database). The security team requires that no internet traffic can reach the Backend subnet directly, but the Frontend subnet must be able to communicate with the Backend subnet on port 1433. Which solution should they implement?
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)
Network Security Groups (NSGs) are the correct solution because they provide stateful, layer-3/4 traffic filtering at the subnet or NIC level. By applying an NSG to the Backend subnet with a rule that denies all inbound internet traffic (deny all from Internet) and a higher-priority rule that allows inbound traffic from the Frontend subnet on TCP port 1433, you enforce the required isolation while permitting necessary SQL communication.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Azure Firewall with a routing table
Why it's wrong here
Azure Firewall is a managed firewall but for subnet-level filtering, NSGs are simpler and more appropriate for this scenario.
✓
Network Security Groups (NSGs)
Why this is correct
NSGs provide stateful filtering at the subnet or NIC level, allowing you to explicitly allow/deny traffic from specific sources.
Related concept
Read the scenario before looking for a memorised answer.
✗
Service Endpoints
Why it's wrong here
Service Endpoints secure connectivity to Azure PaaS services but do not filter all network traffic.
✗
Virtual Network Peering
Why it's wrong here
VNet peering connects VNets, it does not filter traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Service Endpoints with network security filtering, but Service Endpoints only provide a secure direct path to Azure services, not traffic filtering or internet isolation for the subnet itself.
Trap categories for this question
Scenario analysis trap
Azure Firewall is a managed firewall but for subnet-level filtering, NSGs are simpler and more appropriate for this scenario.
Detailed technical explanation
How to think about this question
NSGs use a set of security rules that are evaluated in priority order (lowest number first). Each rule specifies source, destination, protocol, port, and direction (inbound/outbound). By default, NSGs have implicit deny rules at the end, so you only need to explicitly allow the desired Frontend-to-Backend traffic on port 1433 and ensure no rule allows internet inbound. The stateful nature of NSGs means that if you allow inbound traffic from Frontend, the return traffic is automatically permitted without an explicit outbound rule.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-500 question in full detail.
Secure networking — This question tests Secure networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Network Security Groups (NSGs) — Network Security Groups (NSGs) are the correct solution because they provide stateful, layer-3/4 traffic filtering at the subnet or NIC level. By applying an NSG to the Backend subnet with a rule that denies all inbound internet traffic (deny all from Internet) and a higher-priority rule that allows inbound traffic from the Frontend subnet on TCP port 1433, you enforce the required isolation while permitting necessary SQL communication.
What should I do if I get this AZ-500 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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