- A
Add the API VM's NIC to ASG-Api so the NSG rule can match the destination NIC.
Application security groups are assigned to NICs, not to subnets. If the destination NIC is not in ASG-Api, the rule that references ASG-Api never matches, even if the VM sits in the right subnet. Adding the API NIC to the correct ASG allows the NSG rule to evaluate as intended and is the cleanest fix for the blocked 8443 traffic.
- B
Add ASG-Api to the API subnet because ASGs are inherited from subnet membership.
Why wrong: ASGs do not inherit from subnet placement; they must be attached directly to the network interface.
- C
Lower the rule priority number on the web subnet to make source traffic more specific.
Why wrong: The source subnet is already matched correctly; the problem is destination membership, not priority ordering.
- D
Create a user-defined route from AppSubnet to API subnet to bypass the NSG.
Why wrong: Routing does not bypass NSG filtering, so a UDR cannot fix an ASG mismatch.
AZ-104 Implement and Manage Virtual Networking Practice Question
This AZ-104 practice question tests your understanding of implement and manage virtual networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An NSG rule allows TCP 8443 from ASG-Web to ASG-Api on the API subnet. The web VM NIC is already in ASG-Web, but the API VM was only placed in the subnet and not added to ASG-Api. Traffic still fails. What is the best fix?
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
Add the API VM's NIC to ASG-Api so the NSG rule can match the destination NIC.
The NSG rule specifies ASG-Api as the destination, but NSGs evaluate traffic based on the NIC membership in an ASG, not the subnet. Since the API VM's NIC is not added to ASG-Api, the rule cannot match the destination, so traffic is dropped by default (implicit deny). Adding the NIC to ASG-Api allows the NSG rule to correctly identify the destination and permit TCP 8443 traffic.
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.
- ✓
Add the API VM's NIC to ASG-Api so the NSG rule can match the destination NIC.
Why this is correct
Application security groups are assigned to NICs, not to subnets. If the destination NIC is not in ASG-Api, the rule that references ASG-Api never matches, even if the VM sits in the right subnet. Adding the API NIC to the correct ASG allows the NSG rule to evaluate as intended and is the cleanest fix for the blocked 8443 traffic.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Add ASG-Api to the API subnet because ASGs are inherited from subnet membership.
Why it's wrong here
ASGs do not inherit from subnet placement; they must be attached directly to the network interface.
When this WOULD be correct
If the question stated that ASGs are automatically applied to all resources in a subnet (e.g., a hypothetical scenario where ASG membership is inherited from subnet configuration), then adding ASG-Api to the subnet would be the correct fix.
- ✗
Lower the rule priority number on the web subnet to make source traffic more specific.
Why it's wrong here
The source subnet is already matched correctly; the problem is destination membership, not priority ordering.
When this WOULD be correct
In a scenario where multiple NSG rules apply to the same traffic and a lower-priority rule (higher number) is incorrectly blocking traffic, lowering the priority number (making it higher priority) of the correct rule would allow it to override the blocking rule.
- ✗
Create a user-defined route from AppSubnet to API subnet to bypass the NSG.
Why it's wrong here
Routing does not bypass NSG filtering, so a UDR cannot fix an ASG mismatch.
When this WOULD be correct
A question where traffic between subnets is failing due to incorrect routing (e.g., traffic is being sent to a network virtual appliance instead of directly to the destination subnet), and you need to override the default system route with a UDR to force traffic to the correct next hop.
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.
✓Add the API VM's NIC to ASG-Api so the NSG rule can match the destination NIC.Correct answer▾
Why this is correct
Application security groups are assigned to NICs, not to subnets. If the destination NIC is not in ASG-Api, the rule that references ASG-Api never matches, even if the VM sits in the right subnet. Adding the API NIC to the correct ASG allows the NSG rule to evaluate as intended and is the cleanest fix for the blocked 8443 traffic.
✗Add ASG-Api to the API subnet because ASGs are inherited from subnet membership.Wrong answer — click to see why▾
Why this is wrong here
ASGs are not inherited from subnet membership; they must be explicitly assigned to NICs. Adding ASG-Api to the subnet does not associate the API VM's NIC with the ASG, so the NSG rule still cannot match the destination.
★ When this WOULD be the correct answer
If the question stated that ASGs are automatically applied to all resources in a subnet (e.g., a hypothetical scenario where ASG membership is inherited from subnet configuration), then adding ASG-Api to the subnet would be the correct fix.
Why candidates choose this
Candidates may confuse ASGs with NSGs, which are applied at the subnet level, and incorrectly assume that ASGs also propagate from subnet membership.
✗Lower the rule priority number on the web subnet to make source traffic more specific.Wrong answer — click to see why▾
Why this is wrong here
Lowering the rule priority number makes the rule more specific (higher priority), but the issue is that the destination ASG-Api has no members, so the rule cannot match any traffic. Priority does not fix the missing membership.
★ When this WOULD be the correct answer
In a scenario where multiple NSG rules apply to the same traffic and a lower-priority rule (higher number) is incorrectly blocking traffic, lowering the priority number (making it higher priority) of the correct rule would allow it to override the blocking rule.
Why candidates choose this
Candidates may confuse rule priority with rule effectiveness, thinking that making a rule more specific (higher priority) will fix connectivity issues, without realizing that the rule's conditions (like ASG membership) must be met first.
✗Create a user-defined route from AppSubnet to API subnet to bypass the NSG.Wrong answer — click to see why▾
Why this is wrong here
User-defined routes (UDRs) control traffic routing between subnets, not NSG rule evaluation. The issue is that the NSG rule cannot match the destination because the API VM's NIC is not in ASG-Api; a UDR does not fix NSG rule matching.
★ When this WOULD be the correct answer
A question where traffic between subnets is failing due to incorrect routing (e.g., traffic is being sent to a network virtual appliance instead of directly to the destination subnet), and you need to override the default system route with a UDR to force traffic to the correct next hop.
Why candidates choose this
Candidates may confuse NSG rule application with routing, thinking that a UDR can bypass NSG rules or that routing changes can fix application-level connectivity issues caused by NSG misconfigurations.
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 assume subnet membership automatically applies ASG rules, but ASGs require explicit NIC association, and NSG rules with ASG destinations will not match VMs that are only in the subnet.
Detailed technical explanation
How to think about this question
Application Security Groups (ASGs) are evaluated at the NIC level, not the subnet level, and NSG rules with ASG destinations require the destination NIC to be a member of that ASG. Under the hood, Azure's network fabric uses the ASG membership to build flow rules in the virtual switch; if the NIC is not a member, the rule is effectively ignored for that VM. In real-world scenarios, this often occurs when VMs are deployed via scale sets or automation that fails to associate the NIC with the intended ASG, leading to silent traffic drops.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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: Add the API VM's NIC to ASG-Api so the NSG rule can match the destination NIC. — The NSG rule specifies ASG-Api as the destination, but NSGs evaluate traffic based on the NIC membership in an ASG, not the subnet. Since the API VM's NIC is not added to ASG-Api, the rule cannot match the destination, so traffic is dropped by default (implicit deny). Adding the NIC to ASG-Api allows the NSG rule to correctly identify the destination and permit TCP 8443 traffic.
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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