- 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.
Quick Answer
The answer is to add the API VM’s NIC to ASG-Api. This is correct because an NSG rule with an Application Security Group (ASG) as the destination matches traffic based on the NIC’s membership in that ASG, not the subnet the VM resides in. Since the API VM was only placed in the subnet and its NIC was never added to ASG-Api, the rule cannot identify it as a valid destination, and the implicit deny rule drops the TCP 8443 traffic. On the AZ-104 exam, this tests your understanding that ASGs are logical groupings of NICs, not subnets—a common trap is assuming subnet placement alone satisfies an ASG-based rule. Remember: ASGs attach to NICs, not subnets; if the NIC isn’t in the group, the rule won’t match. A helpful memory tip is “NIC in the group, or the rule goes poof.”
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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.
Clue confirmation
The clue word "best" in the question point toward this answer.
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.
- ✗
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.
- ✗
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.
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.
What to study next
Got this wrong? Here's your next step.
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Implement and Manage Virtual Networking — study guide chapter
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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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on AZ-104
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An NSG outbound rule allows TCP 8443 traffic from ASG-Web to ASG-Api. The web VM NIC is in ASG-Web, but the API VM NICs were deployed into the correct subnet and never added to ASG-Api. The traffic still fails. What should the administrator do?
medium- A.Move the NSG to the web subnet so source membership is automatically detected.
- ✓ B.Add the API VM NICs to ASG-Api.
- C.Change the destination port to 443 because ASGs only work with common HTTPS traffic.
- D.Create a service endpoint for the spoke subnet so the NSG rule becomes effective.
Why B: The NSG rule references ASG-Api as the destination, but the API VM NICs were never added to that application security group. ASGs are logical groupings of VM NICs; a rule targeting an ASG only applies to NICs that are members of that ASG. Since the API NICs are not in ASG-Api, the rule does not match them, and traffic fails. Adding the API VM NICs to ASG-Api resolves the issue by making them valid destinations for the rule.
Last reviewed: Jun 11, 2026
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.
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