The answer is Application Security Groups (ASGs) for the frontend and backend VMs. This is correct because ASGs enable tier isolation within the same subnet by grouping VMs logically by function—such as frontend and backend—allowing you to create a single NSG rule that references these groups as source and destination, restricting traffic to TCP 443 without ever needing to specify individual VM IP addresses. On the AZ-104 exam, this scenario tests your understanding of how ASGs decouple network security from network topology, a common trap being that many candidates mistakenly reach for Network Security Groups with IP-based rules or service tags, which cannot isolate tiers within the same subnet. Remember the key distinction: ASGs work at the VM network interface level, not the subnet level, making them ideal for micro-segmentation inside a shared subnet. A helpful memory tip is to think of ASGs as “logical team jerseys” for your VMs—you write one rule for the whole team, not for each player.
AZ-104 Implement and Manage Virtual Networking Practice Question
This AZ-104 practice question tests your understanding of implement and manage virtual 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 company has frontend and backend VMs in the same subnet. Security rules must allow the frontend tier to reach only the backend tier on TCP 443, without assigning rules to individual VM IP addresses. What should the administrator use in the NSG rule?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Application security groups for the frontend and backend VMs.
Option C is correct because Application Security Groups (ASGs) allow you to group VMs logically by their application tier (e.g., frontend, backend) without relying on individual IP addresses. You can then create an NSG rule that uses the frontend ASG as the source and the backend ASG as the destination, restricting traffic to TCP 443. This meets the requirement of not assigning rules to individual VMIPs while ensuring only frontend VMs can reach backend VMs within the same subnet.
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.
✗
A user-defined route that sends frontend traffic to the backend subnet.
Why it's wrong here
Routes control next hop selection, not fine-grained east-west access rules.
✗
A network security group rule that references both subnets by address prefix only.
Why it's wrong here
Subnet prefixes are broader than required and do not identify application tiers cleanly.
✓
Application security groups for the frontend and backend VMs.
Why this is correct
ASGs let you group VMs by workload role and reference those groups in NSG rules.
Related concept
Read the scenario before looking for a memorised answer.
✗
A VNet peering connection between the two tiers.
Why it's wrong here
Peering is for separate VNets, not for separating roles inside one subnet.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume subnet-based NSG rules are sufficient for tier isolation, but since both tiers share the same subnet, a subnet-to-subnet rule would allow all VMs in that subnet to communicate, failing the requirement to restrict traffic to only frontend-to-backend on TCP 443.
Detailed technical explanation
How to think about this question
Application Security Groups work at the network interface level, not the subnet level, allowing dynamic membership based on VM tags. When an NSG rule references an ASG, Azure translates the ASG to the set of private IP addresses of the attached NICs at runtime, enabling granular security without static IP management. A real-world scenario is a multi-tier application where VMs are auto-scaled; ASGs automatically include new instances without updating NSG rules, unlike subnet-based rules that would require subnet segmentation.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-104 question in full detail.
Implement and Manage Virtual Networking — This question tests Implement and Manage Virtual Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Application security groups for the frontend and backend VMs. — Option C is correct because Application Security Groups (ASGs) allow you to group VMs logically by their application tier (e.g., frontend, backend) without relying on individual IP addresses. You can then create an NSG rule that uses the frontend ASG as the source and the backend ASG as the destination, restricting traffic to TCP 443. This meets the requirement of not assigning rules to individual VM IPs while ensuring only frontend VMs can reach backend VMs within the same subnet.
What should I do if I get this AZ-104 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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