- A
The backend subnet CIDR, because subnet ranges never change during VM rebuilds.
Why wrong: A subnet CIDR is broader than the individual backend members and does not model the application tier as cleanly as an ASG. It also does not solve later tier-to-tier reuse as well as security groups do.
- B
The AzureLoadBalancer service tag, because it identifies internal traffic between tiers.
Why wrong: AzureLoadBalancer is only for Azure load balancer probe traffic. It does not represent the web tier or the backend tier in this scenario.
- C
Application security groups for both tiers, because they track the VMs even when IP addresses change.
Application security groups let you group NICs by application role instead of by changing IP addresses. By referencing ASG-Web as the source and ASG-Backend as the destination, the NSG rule stays stable when backend VMs are rebuilt or NICs are replaced. This is the most maintainable option for tier-based filtering on a fixed port.
- D
A user-defined route to the backend subnet, because route tables follow the VM even if the IP changes.
Why wrong: Route tables control traffic forwarding, not security filtering. They cannot replace NSG rules for allowing a specific TCP port between tiers.
AZ-104 Implement and Manage Virtual Networking Practice Question
This AZ-104 practice question tests your understanding of implement and manage virtual networking. 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.
A web tier and a backend tier are deployed in separate subnets. Backend VMs are rebuilt regularly, so their private IP addresses change. The web tier must reach the backend on TCP 8443, and administrators do not want to update NSG rules whenever a backend VM is replaced. What should be used in the NSG rule?
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
Application security groups for both tiers, because they track the VMs even when IP addresses change.
Option C is correct because Application Security Groups (ASGs) allow you to group VMs logically and reference them in NSG rules. When backend VMs are rebuilt and their private IPs change, the ASG membership (based on the VM's NIC configuration) remains intact, so the NSG rule continues to apply without manual updates. This decouples security rules from dynamic IP addresses.
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.
- ✗
The backend subnet CIDR, because subnet ranges never change during VM rebuilds.
Why it's wrong here
A subnet CIDR is broader than the individual backend members and does not model the application tier as cleanly as an ASG. It also does not solve later tier-to-tier reuse as well as security groups do.
When this WOULD be correct
This option would be correct if the question required restricting traffic to a specific set of backend VMs that are not all in the same subnet, or if the subnet contained other VMs that should not be accessed. For example: 'Backend VMs are in a subnet that also hosts management VMs. Web tier must only reach backend VMs on TCP 8443, and backend VMs are rebuilt with new IPs. What should be used in the NSG rule?' In that case, using the subnet CIDR would allow traffic to all VMs in the subnet, which is not desired.
- ✗
The AzureLoadBalancer service tag, because it identifies internal traffic between tiers.
Why it's wrong here
AzureLoadBalancer is only for Azure load balancer probe traffic. It does not represent the web tier or the backend tier in this scenario.
When this WOULD be correct
In a scenario where the web tier needs to allow health probe traffic from Azure Load Balancer to the backend VMs (e.g., on TCP 80 or 443), using the AzureLoadBalancer service tag in an NSG rule would be correct to permit that specific traffic.
- ✓
Application security groups for both tiers, because they track the VMs even when IP addresses change.
Why this is correct
Application security groups let you group NICs by application role instead of by changing IP addresses. By referencing ASG-Web as the source and ASG-Backend as the destination, the NSG rule stays stable when backend VMs are rebuilt or NICs are replaced. This is the most maintainable option for tier-based filtering on a fixed port.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A user-defined route to the backend subnet, because route tables follow the VM even if the IP changes.
Why it's wrong here
Route tables control traffic forwarding, not security filtering. They cannot replace NSG rules for allowing a specific TCP port between tiers.
When this WOULD be correct
A question where administrators need to force traffic from the web tier to the backend tier through a network virtual appliance (NVA) for inspection, regardless of backend IP changes. In that case, a UDR on the web subnet with the backend subnet as destination and the NVA as next hop would be correct.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-104 exam frequently reuses these exact scenarios with slightly different constraints.
✓Application security groups for both tiers, because they track the VMs even when IP addresses change.Correct answer▾
Why this is correct
Application security groups let you group NICs by application role instead of by changing IP addresses. By referencing ASG-Web as the source and ASG-Backend as the destination, the NSG rule stays stable when backend VMs are rebuilt or NICs are replaced. This is the most maintainable option for tier-based filtering on a fixed port.
✗The backend subnet CIDR, because subnet ranges never change during VM rebuilds.Wrong answer — click to see why▾
Why this is wrong here
The backend subnet CIDR is static, but the question states that backend VMs are rebuilt regularly and their private IP addresses change. An NSG rule using the subnet CIDR would still allow traffic to any VM in that subnet, including rebuilt ones, so it would actually work. However, the question specifies that administrators do not want to update NSG rules, and using the subnet CIDR does not require updates. The correct answer is C because application security groups provide a more granular and dynamic way to group VMs regardless of IP changes. Option A is not wrong in functionality; it is less preferred because it is broader and less secure than using ASGs, but the question's phrasing may mislead.
★ When this WOULD be the correct answer
This option would be correct if the question required restricting traffic to a specific set of backend VMs that are not all in the same subnet, or if the subnet contained other VMs that should not be accessed. For example: 'Backend VMs are in a subnet that also hosts management VMs. Web tier must only reach backend VMs on TCP 8443, and backend VMs are rebuilt with new IPs. What should be used in the NSG rule?' In that case, using the subnet CIDR would allow traffic to all VMs in the subnet, which is not desired.
Why candidates choose this
Candidates may think that because IPs change, a static CIDR rule would need constant updates, but actually the subnet CIDR remains the same even if individual VM IPs change. They overlook that the subnet CIDR is a range that covers all possible IPs in that subnet, so it still works without updates.
✗The AzureLoadBalancer service tag, because it identifies internal traffic between tiers.Wrong answer — click to see why▾
Why this is wrong here
The AzureLoadBalancer service tag identifies traffic from the Azure load balancer health probes, not general inter-tier traffic. It does not cover traffic from web VMs to backend VMs, so it cannot be used to allow TCP 8443 between tiers.
★ When this WOULD be the correct answer
In a scenario where the web tier needs to allow health probe traffic from Azure Load Balancer to the backend VMs (e.g., on TCP 80 or 443), using the AzureLoadBalancer service tag in an NSG rule would be correct to permit that specific traffic.
Why candidates choose this
Candidates may confuse the AzureLoadBalancer service tag with a general-purpose tag for internal traffic, or think it represents all traffic between tiers because load balancers are often used to route traffic between tiers.
✗A user-defined route to the backend subnet, because route tables follow the VM even if the IP changes.Wrong answer — click to see why▾
Why this is wrong here
User-defined routes (UDRs) control traffic routing, not NSG rule matching. NSG rules use source/destination IPs, service tags, or application security groups, not route tables. A UDR cannot be used as a source or destination in an NSG rule.
★ When this WOULD be the correct answer
A question where administrators need to force traffic from the web tier to the backend tier through a network virtual appliance (NVA) for inspection, regardless of backend IP changes. In that case, a UDR on the web subnet with the backend subnet as destination and the NVA as next hop would be correct.
Why candidates choose this
Candidates may confuse routing (UDRs) with security filtering (NSGs), thinking that a route can substitute for an NSG rule when IPs are dynamic, or they may believe that route tables can be referenced in NSG rules.
Analysis generated from the official AZ-104blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse service tags (which identify Azure services) with ASGs (which identify application tiers), or they assume subnet CIDRs are always the best choice despite the requirement for dynamic IP handling.
Trap categories for this question
Scenario analysis trap
AzureLoadBalancer is only for Azure load balancer probe traffic. It does not represent the web tier or the backend tier in this scenario.
Detailed technical explanation
How to think about this question
Application Security Groups work at the NIC level; when a VM is rebuilt, its new NIC can be assigned to the same ASG via ARM templates or scripts, ensuring the NSG rule referencing that ASG remains valid. Under the hood, ASGs are evaluated as part of the NSG's five-tuple rule processing, and they support up to 3000 IP configurations per ASG. In a real-world scenario, using ASGs with Azure DevOps or Terraform allows zero-touch security updates during auto-scaling or patching cycles.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this AZ-104 question test?
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 both tiers, because they track the VMs even when IP addresses change. — Option C is correct because Application Security Groups (ASGs) allow you to group VMs logically and reference them in NSG rules. When backend VMs are rebuilt and their private IPs change, the ASG membership (based on the VM's NIC configuration) remains intact, so the NSG rule continues to apply without manual updates. This decouples security rules from dynamic IP addresses.
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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Last reviewed: Jun 11, 2026
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