- A
Azure Virtual Network with subnets for each tier and Network Security Groups.
This is the standard and most cost-effective approach. Subnets provide logical isolation, and NSGs enforce inbound/outbound rules. Internet traffic can be allowed only to the web subnet via a public IP and NSG rules.
- B
Azure Virtual Network with a single subnet and application security groups.
Why wrong: A single subnet does not provide network-level isolation between tiers. Application Security Groups (ASGs) can help, but they are not a substitute for subnet-level security boundaries.
- C
Azure Virtual Network with subnets and Azure Firewall.
Why wrong: Azure Firewall is a managed, cloud-native network security service for perimeter protection. While it can filter traffic, placing it between subnets adds unnecessary cost and complexity for internal tier isolation; NSGs are more appropriate.
- D
Azure Virtual Network with subnets and a network virtual appliance (NVA).
Why wrong: An NVA can provide advanced inspection but is unnecessary for the stated requirement for simple tier isolation. NSGs are simpler and more cost-effective for this scenario.
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.
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?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Azure Virtual Network with subnets for each tier and Network Security Groups.
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.
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 Virtual Network with subnets for each tier and Network Security Groups.
Why this is correct
This is the standard and most cost-effective approach. Subnets provide logical isolation, and NSGs enforce inbound/outbound rules. Internet traffic can be allowed only to the web subnet via a public IP and NSG rules.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Azure Virtual Network with a single subnet and application security groups.
Why it's wrong here
A single subnet does not provide network-level isolation between tiers. Application Security Groups (ASGs) can help, but they are not a substitute for subnet-level security boundaries.
- ✗
Azure Virtual Network with subnets and Azure Firewall.
Why it's wrong here
Azure Firewall is a managed, cloud-native network security service for perimeter protection. While it can filter traffic, placing it between subnets adds unnecessary cost and complexity for internal tier isolation; NSGs are more appropriate.
- ✗
Azure Virtual Network with subnets and a network virtual appliance (NVA).
Why it's wrong here
An NVA can provide advanced inspection but is unnecessary for the stated requirement for simple tier isolation. NSGs are simpler and more cost-effective for this scenario.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often over-engineer the solution by choosing Azure Firewall or an NVA for basic isolation, not realizing that NSGs with subnets are the native, cost-effective, and fully supported method for network segmentation within a single Azure VNet.
Trap categories for this question
Scenario analysis trap
An NVA can provide advanced inspection but is unnecessary for the stated requirement for simple tier isolation. NSGs are simpler and more cost-effective for this scenario.
Detailed technical explanation
How to think about this question
Azure NSGs are stateful and process rules in priority order, allowing you to explicitly allow or deny traffic based on source/destination IP, port, and protocol (TCP/UDP/ICMP). When combined with service tags (e.g., Internet, VirtualNetwork) and application security groups, NSGs can enforce zero-trust micro-segmentation without requiring a separate firewall. In a three-tier architecture, the database subnet typically denies all inbound traffic except from the application subnet’s IP range, and the application subnet denies all inbound except from the web subnet, while the web subnet allows inbound on ports 80/443 from the Internet tag.
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 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.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this AZ-305 question test?
Design infrastructure solutions — This question tests Design infrastructure solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Virtual Network with subnets for each tier and Network Security Groups. — 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.
What should I do if I get this AZ-305 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.
About these practice questions
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Last reviewed: Jun 11, 2026
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