AZ-104 Implement and Manage Virtual Networking Practice Question
A backend tier runs on three Azure VMs. The VMs are rebuilt frequently and receive new private IP addresses during redeployment. The administrator must allow inbound TCP 1433 from the app tier without rewriting the NSG rule each time the backend VMs change. What should be used?
⚠ Common exam trap
Many candidates confuse application security groups with network security groups or think that a load balancer or service endpoint can solve dynamic IP changes, but only ASGs provide a logical grouping that automatically follows VM IP changes without manual rule updates.
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
✓
An application security group referenced by the NSG rule
An application security group (ASG) allows you to group VMs logically (e.g., by tier) and reference that group in a network security group (NSG) rule. When backend VMs are rebuilt and receive new private IPs, the ASG membership is automatically updated, so the NSG rule continues to apply without manual changes. This makes ASG the correct choice for dynamic environments where IP addresses change frequently.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Individual private IP addresses assigned directly in the NSG rule
Why it's wrong here
Hard-coding individual private IP addresses in an NSG rule only works while those addresses are stable and known in advance. If the VMs are rebuilt, Azure typically assigns new private IPs, or if you force static IPs you must manually edit every rule after each rebuild, making this approach brittle and high-maintenance. It also fails to capture the backend tier as a logical unit, so adding or removing a VM requires rewriting security rules.
When this WOULD be correct
If the backend VMs had static private IP addresses that never change, assigning those IPs directly in an NSG rule would be a valid approach to allow inbound traffic from the app tier.
- ✓
An application security group referenced by the NSG rule
Why this is correct
Application security groups let you group VMs logically and reference that group in NSG rules. When the backend VMs are rebuilt or their IPs change, the rule still applies as long as the NICs remain members of the ASG, which reduces manual maintenance.
- ✗
A service endpoint enabled on the subnet
Why it's wrong here
A service endpoint extends a subnet's routing to secure connectivity to supported Azure PaaS services (such as Azure SQL Database or Storage), but it does not act as an NSG source/destination and does not group VMs. Even with the endpoint enabled, a backend-tier NSG rule still needs an explicit source or destination construct; the endpoint only prevents traffic to that PaaS service from leaving the Microsoft backbone. Thus it doesn't help when rebuilt VMs need to be targeted as a group.
When this WOULD be correct
A question where the backend tier is an Azure SQL Database (PaaS) instead of VMs, and the requirement is to restrict access from a specific subnet to the database. In that case, enabling a service endpoint on the subnet and creating a firewall rule for the subnet would be correct.
- ✗
A load balancer inbound NAT rule on port 1433
Why it's wrong here
An inbound NAT rule on a load balancer maps a specific frontend port to a designated port on a single VM, and it exists to reach an individual instance (for example, RDP/SSH), not to express a security rule for an entire tier. On port 1433 it might expose SQL Server instances, but it neither groups the backend VMs nor makes them easier to reference in an NSG after a rebuild. NAT rules work in combination with NSGs, but they do not simplify the NSG rule itself.
When this WOULD be correct
A load balancer inbound NAT rule would be correct if the question required mapping a single public port to a specific backend VM for RDP/SSH access, and the backend VMs had static private IPs or the NAT rule was dynamically updated via automation.
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.
✓An application security group referenced by the NSG ruleCorrect answer▾
Why this is correct
Application security groups let you group VMs logically and reference that group in NSG rules. When the backend VMs are rebuilt or their IPs change, the rule still applies as long as the NICs remain members of the ASG, which reduces manual maintenance.
✗Individual private IP addresses assigned directly in the NSG ruleWrong answer — click to see why▾
Why this is wrong here
Individual private IP addresses change each time the VMs are rebuilt, requiring NSG rule updates. This does not meet the requirement to avoid rewriting rules.
★ When this WOULD be the correct answer
If the backend VMs had static private IP addresses that never change, assigning those IPs directly in an NSG rule would be a valid approach to allow inbound traffic from the app tier.
Why candidates choose this
Candidates may think that specifying IP addresses directly is the most straightforward way to control access, overlooking the dynamic nature of the IPs in this scenario.
✗A service endpoint enabled on the subnetWrong answer — click to see why▾
Why this is wrong here
A service endpoint secures Azure service access from a subnet to a specific service (e.g., Azure SQL Database) and does not filter traffic between VMs within a VNet. It cannot be used to allow inbound TCP 1433 from the app tier to backend VMs with dynamic private IPs.
★ When this WOULD be the correct answer
A question where the backend tier is an Azure SQL Database (PaaS) instead of VMs, and the requirement is to restrict access from a specific subnet to the database. In that case, enabling a service endpoint on the subnet and creating a firewall rule for the subnet would be correct.
Why candidates choose this
Candidates may confuse service endpoints with network security groups, thinking they can filter traffic between VMs. They might also recall that service endpoints improve security for Azure services and incorrectly assume they can replace NSG rules for VM-to-VM traffic.
✗A load balancer inbound NAT rule on port 1433Wrong answer — click to see why▾
Why this is wrong here
A load balancer inbound NAT rule translates a specific frontend port to a backend VM's private IP and port, but it does not solve the problem of changing private IPs because the NAT rule must be updated each time the backend VM's IP changes, which is the same rewriting issue the question aims to avoid.
★ When this WOULD be the correct answer
A load balancer inbound NAT rule would be correct if the question required mapping a single public port to a specific backend VM for RDP/SSH access, and the backend VMs had static private IPs or the NAT rule was dynamically updated via automation.
Why candidates choose this
Candidates may think a load balancer can handle changing IPs automatically, but inbound NAT rules are static mappings; they confuse load balancing (which distributes traffic) with NAT rules (which target specific VMs).
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?”
Go deeper
Related to this question
Learn chapter
Dynamic Membership Groups
Key term
Group
A group is a collection of users, devices, or other objects that are assigned permissions and policies together for simplified management in identity and governance systems like Microsoft Entra ID.
Key term
ASG
An Availability Set is a logical grouping of virtual machines in Azure that helps ensure high availability by distributing VMs across different physical hardware within a datacenter.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-104 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-104 exam.