- A
The allow rule wins because subnet NSGs always override NIC NSGs.
Why wrong: Subnet NSGs do not automatically override NIC NSGs. Both scopes are evaluated, and a deny at either scope blocks the traffic.
- B
The traffic is blocked because a deny in either NSG is effective.
Azure evaluates both NIC and subnet NSGs. If either one denies the packet, the connection is blocked even if the other NSG has an allow rule.
- C
The traffic is allowed because service tags bypass NIC-level rules.
Why wrong: Service tags simplify rule targeting, but they do not bypass evaluation or ignore a deny rule at another NSG scope.
- D
The connection succeeds unless a route table sends the traffic elsewhere.
Why wrong: Routing affects the path, not the security decision. NSG denies are enforced independently of route table configuration.
Quick Answer
The answer is that the traffic is blocked because a deny rule in either NSG is effective. This occurs because when both a subnet-level NSG and a NIC-level NSG are applied, Azure evaluates traffic against both, and the most restrictive rule wins—meaning any explicit deny overrides any allow. In this scenario, the NIC-level NSG denies inbound TCP 22 from the VirtualNetwork service tag, so even though the subnet NSG allows it, the deny at the NIC level takes precedence and the traffic is blocked. On the AZ-104 exam, this tests your understanding of NSG rule precedence and the common trap that subnet rules are sufficient; in reality, a deny at either level is final. Remember the memory tip: "One deny, all deny"—if either NSG says no, the traffic stops.
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 VM in a subnet has both a subnet-level NSG and a NIC-level NSG. The subnet NSG allows inbound TCP 22 from the VirtualNetwork service tag, but the NIC NSG denies inbound TCP 22 from the same source. An administrator says the subnet rule should be enough because it allows the traffic. What is the actual behavior?
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
The traffic is blocked because a deny in either NSG is effective.
When both a subnet-level NSG and a NIC-level NSG are applied to a virtual machine, network traffic is evaluated against both NSGs. The effective rule is the most restrictive: if either NSG contains a deny rule that matches the traffic, the traffic is blocked. In this scenario, the NIC-level NSG explicitly denies inbound TCP 22 from the VirtualNetwork service tag, so even though the subnet NSG allows it, the deny at the NIC level takes precedence and the traffic is blocked.
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 allow rule wins because subnet NSGs always override NIC NSGs.
Why it's wrong here
Subnet NSGs do not automatically override NIC NSGs. Both scopes are evaluated, and a deny at either scope blocks the traffic.
- ✓
The traffic is blocked because a deny in either NSG is effective.
Why this is correct
Azure evaluates both NIC and subnet NSGs. If either one denies the packet, the connection is blocked even if the other NSG has an allow rule.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The traffic is allowed because service tags bypass NIC-level rules.
Why it's wrong here
Service tags simplify rule targeting, but they do not bypass evaluation or ignore a deny rule at another NSG scope.
- ✗
The connection succeeds unless a route table sends the traffic elsewhere.
Why it's wrong here
Routing affects the path, not the security decision. NSG denies are enforced independently of route table configuration.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume subnet-level NSGs take precedence over NIC-level NSGs, but Azure actually applies both and the most restrictive rule (any deny) wins, making it critical to check both NSGs for conflicting rules.
Detailed technical explanation
How to think about this question
Azure NSGs are stateful and rules are evaluated in priority order (lowest number first) within each NSG. When both a subnet and NIC NSG are applied, the effective security rules are the union of both sets, with the most restrictive outcome applied. This behavior is documented in Azure's network security group evaluation logic, where traffic must pass both NSGs to be allowed. In practice, this means an administrator must carefully coordinate rules across both NSG levels to avoid unintended blocks.
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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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: The traffic is blocked because a deny in either NSG is effective. — When both a subnet-level NSG and a NIC-level NSG are applied to a virtual machine, network traffic is evaluated against both NSGs. The effective rule is the most restrictive: if either NSG contains a deny rule that matches the traffic, the traffic is blocked. In this scenario, the NIC-level NSG explicitly denies inbound TCP 22 from the VirtualNetwork service tag, so even though the subnet NSG allows it, the deny at the NIC level takes precedence and the traffic is blocked.
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.
About these practice questions
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Last reviewed: Jun 11, 2026
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