The correct answer is Azure Application Gateway with WAF for the front-end, NSGs on subnets, and service endpoints. This combination works because the Application Gateway with WAF provides internet-facing access and web application firewall protection for the front-end tier, while Network Security Groups (NSGs) applied to each subnet enforce strict east-west traffic isolation—allowing the business tier to only receive traffic from the front-end subnet and the data tier to only communicate with the business subnet. Service endpoints further secure Azure PaaS services by restricting access to specific subnets, minimizing exposure without additional appliances. On the AZ-305 exam, this scenario tests your ability to choose the simplest Azure-native isolation pattern for a three-tier network architecture, often appearing as a trap where candidates over-engineer with Azure Firewall or misapply load balancers. A common memory tip is “GW for the web, NSGs for the mesh, endpoints for the PaaS”—remember that Azure Firewall is overkill for simple subnet-to-subnet rules, and Application Gateway is the only front-end service that natively includes WAF.
AZ-305 Design infrastructure solutions Practice Question
This AZ-305 practice question tests your understanding of design infrastructure solutions. 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 designing a network architecture for a three-tier application hosted in Azure. The front-end tier must be accessible from the internet, the business tier must only communicate with the front-end tier, and the data tier must only communicate with the business tier. You need to minimize exposure and use Azure-native services. Which combination of services should you use?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Application Gateway with WAF for front-end, NSGs on subnets, and service endpoints
Azure Application Gateway with WAF provides internet-facing front-end with web firewall. Network Security Groups (NSGs) on subnets restrict traffic between tiers. Option A (Azure Load Balancer) lacks WAF. Option C (Azure Firewall) is overkill for simple tier isolation. Option D (VPN Gateway) is for on-premises connectivity, not internal 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.
✗
Azure Load Balancer for front-end, NSGs on subnets, and VNet peering
Why it's wrong here
Azure Load Balancer does not provide application-layer protection like WAF.
✗
VPN Gateway for front-end, NSGs on subnets, and private endpoints
Why it's wrong here
VPNGateway is for site-to-site connectivity, not public internet access.
✓
Azure Application Gateway with WAF for front-end, NSGs on subnets, and service endpoints
Azure Firewall for all inbound traffic, NSGs on subnets, and VNet peering
Why it's wrong here
Azure Firewall is a stateful firewall but not optimized for web traffic; also more costly.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-305 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-305 subnetting questions on CIDR, address ranges, and subnet selection.
Design infrastructure solutions — This question tests Design infrastructure solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Azure Application Gateway with WAF for front-end, NSGs on subnets, and service endpoints — Azure Application Gateway with WAF provides internet-facing front-end with web firewall. Network Security Groups (NSGs) on subnets restrict traffic between tiers. Option A (Azure Load Balancer) lacks WAF. Option C (Azure Firewall) is overkill for simple tier isolation. Option D (VPN Gateway) is for on-premises connectivity, not internal isolation.
What should I do if I get this AZ-305 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-305 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. You are designing a network architecture for a three-tier application in Azure. The web tier must be accessible from the internet. The application tier must only accept traffic from the web tier. The database tier must only accept traffic from the application tier. Which TWO Azure services should you use to enforce these network rules? (Choose two.)
easy
A.Azure Bastion
✓ B.Network Security Groups (NSGs)
✓ C.Azure Application Gateway
D.Azure Front Door
E.Azure Firewall
Why B: Options A and D are correct. Azure Application Gateway provides web traffic routing and WAF. Network Security Groups (NSGs) allow inbound/outbound rules to restrict traffic between tiers. Option B is wrong because Azure Firewall is a stateful firewall but not needed for simple tier isolation. Option C is wrong because Azure Bastion is for RDP/SSH access. Option E is wrong because Azure Front Door is for global load balancing.
Variation 2. A company is designing a virtual network architecture for a three-tier application (web, application, database). They want network isolation between tiers and secure access from the internet to the web tier only. Which Azure networking solution should they use?
easy
✓ A.Azure Virtual Network with subnets for each tier and Network Security Groups.
B.Azure Virtual Network with a single subnet and application security groups.
C.Azure Virtual Network with subnets and Azure Firewall.
D.Azure Virtual Network with subnets and a network virtual appliance (NVA).
Why A: Option A is correct because deploying each tier in its own subnet within an Azure Virtual Network and applying Network Security Groups (NSGs) allows granular inbound/outbound rule enforcement. NSGs can restrict traffic so that only the web tier is reachable from the internet (via a public IP or Azure Load Balancer), while the application and database tiers are isolated from direct internet access and can only communicate with the adjacent tier as defined by NSG rules.
Variation 3. You need to design a virtual network architecture for a three-tier application in Azure. The web tier must be accessible from the internet, the application tier must only be accessible from the web tier, and the database tier must only be accessible from the application tier. Which combination of Azure services should you use?
easy
A.Use Azure Front Door, service endpoints, and Azure SQL Database with firewall rules.
✓ B.Use Azure Application Gateway with WAF, network security groups (NSGs) on subnets, and Azure Private Endpoints for the database.
C.Use Azure Load Balancer, Azure Firewall, and Azure SQL Database with public endpoint.
D.Use a single virtual network with three subnets, no NSGs, and Azure SQL Database with VNet injection.
Why B: Option A is correct because it uses Azure Application Gateway for inbound internet traffic with WAF, NSGs to restrict traffic between tiers, and Private Endpoints for database access. Option B is wrong because Azure Load Balancer does not provide WAF or path-based routing. Option C is wrong because Azure Front Door is a global service, not for internal VNet traffic. Option D is wrong because placing all VMs in same subnet violates security.
Last reviewed: Jun 20, 2026
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