The correct answer is to enable Service Endpoints for the web app and configure the Application Gateway with a private IP. This configuration ensures that all traffic between the Application Gateway and the web app stays on the Azure backbone network by restricting the web app to accept traffic only from the Application Gateway’s subnet via the Service Endpoint, while the private IP on the gateway eliminates any public internet hop. On the AZ-305 exam, this scenario tests your understanding of network isolation patterns for PaaS services, often appearing as a trap where candidates over-engineer with Private Link or Azure Firewall when a simpler Service Endpoint suffices. A common memory tip is “Private IP + Service Endpoint = backbone-only path,” contrasting with Private Link’s use for outbound or cross-tenant scenarios. Remember, for keeping traffic on the Azure backbone between Application Gateway and App Service, Service Endpoints are the lightweight, exam-preferred choice.
AZ-305 Design infrastructure solutions Practice Question
This AZ-305 practice question tests your understanding of design infrastructure solutions. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 multi-tier application. The front-end tier is an Azure Application Gateway that routes traffic to a web app on Azure App Service. The back-end tier is an Azure SQL Database. You need to ensure that all traffic between the Application Gateway and the web app remains within the Azure backbone network, and that the web app can only be accessed through the Application Gateway. What should you configure?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable Service Endpoints for the web app and configure the Application Gateway with a private IP.
Option C is correct because enabling Service Endpoints for the web app's subnet restricts access to that subnet, and configuring the Application Gateway to use a private IP ensures traffic stays within Azure. App Service can be integrated with a VNet via regional VNet integration, but Service Endpoints are simpler for this scenario. Option A (Azure Firewall) is not needed. Option B (VPN Gateway) is for hybrid connectivity. Option D (Private Link) is more complex and used for PaaS services; Service Endpoints are sufficient.
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 Azure Private Link for the web app and disable public access.
Why it's wrong here
Private Link is an option but more complex; Service Endpoints are simpler and sufficient.
✓
Enable Service Endpoints for the web app and configure the Application Gateway with a private IP.
Why this is correct
Service Endpoints ensure traffic stays on Azure backbone; private IP restricts access to the gateway.
Deploy Azure Firewall in front of the Application Gateway.
Why it's wrong here
Azure Firewall adds cost and complexity; not needed for this scenario.
✗
Use a site-to-site VPN between the App Service and Application Gateway.
Why it's wrong here
VPN is for on-premises connectivity, not between Azure services.
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.
Trap categories for this question
Scenario analysis trap
Azure Firewall adds cost and complexity; not needed for this scenario.
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: Enable Service Endpoints for the web app and configure the Application Gateway with a private IP. — Option C is correct because enabling Service Endpoints for the web app's subnet restricts access to that subnet, and configuring the Application Gateway to use a private IP ensures traffic stays within Azure. App Service can be integrated with a VNet via regional VNet integration, but Service Endpoints are simpler for this scenario. Option A (Azure Firewall) is not needed. Option B (VPN Gateway) is for hybrid connectivity. Option D (Private Link) is more complex and used for PaaS services; Service Endpoints are sufficient.
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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