- A
Whether the NSG has an outbound deny rule for port 80.
Why wrong: An NSG can block traffic, but the symptom here is that the UDR is not being used at all.
- B
Whether the route table is associated with the correct subnet.
A route table only affects traffic for the subnet to which it is associated. If the table exists and the route is correct but traffic still follows another path, the first thing to verify is that the VM's subnet is actually linked to that route table. Without that association, the UDR is never applied, even though the route definition itself looks valid.
- C
Whether the VM uses a managed identity.
Why wrong: Managed identities are unrelated to routing behavior and do not influence packet forwarding decisions.
- D
Whether the virtual machine is in an availability set.
Why wrong: Availability sets improve resilience, but they do not determine whether a UDR is applied to a subnet.
Quick Answer
The answer is to check whether the route table is associated with the correct subnet. Even if your User Defined Route (UDR) contents are perfectly configured with the correct prefix and next hop type of Virtual appliance, Azure’s default system routes will still apply to any subnet that lacks an explicit route table association. The route table is just a set of rules; it only overrides default behavior when it is linked to a specific subnet. On the AZ-104 exam, this is a classic trap—candidates often troubleshoot the UDR rules themselves, forgetting that association is a separate, required step. The question tests your understanding that routing in Azure is subnet-scoped, not VM-scoped. To remember this, use the mnemonic: “No link, no think”—if the route table isn’t linked to the subnet, the VM won’t think to use the custom route. Always verify the subnet’s “Route table” property first when a UDR is not working.
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. A key principle to apply: user-Defined Routes (UDRs) override Azure's default system routes.. 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 administrator creates a route table with a UDR for 10.20.0.0/16 and next hop type Virtual appliance. A VM in the subnet still does not send that traffic to the appliance. The route table contents are correct. What should be checked first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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
Whether the route table is associated with the correct subnet.
The most common reason a UDR fails to take effect is that the route table is not associated with the subnet containing the VM. Even if the route table contents are correct, the VM's traffic will follow default system routes unless the route table is explicitly linked to the subnet. Association is a required step to override Azure's default routing behavior.
Key principle: User-Defined Routes (UDRs) override Azure's default system routes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Whether the NSG has an outbound deny rule for port 80.
Why it's wrong here
An NSG can block traffic, but the symptom here is that the UDR is not being used at all.
- ✓
Whether the route table is associated with the correct subnet.
Why this is correct
A route table only affects traffic for the subnet to which it is associated. If the table exists and the route is correct but traffic still follows another path, the first thing to verify is that the VM's subnet is actually linked to that route table. Without that association, the UDR is never applied, even though the route definition itself looks valid.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
User-Defined Routes (UDRs) override Azure's default system routes.
- ✗
Whether the VM uses a managed identity.
Why it's wrong here
Managed identities are unrelated to routing behavior and do not influence packet forwarding decisions.
- ✗
Whether the virtual machine is in an availability set.
Why it's wrong here
Availability sets improve resilience, but they do not determine whether a UDR is applied to a subnet.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often focus on the route table contents being correct and overlook the critical step of associating the route table with the subnet, assuming that creating the route table is sufficient to apply it.
Detailed technical explanation
How to think about this question
Route tables are applied at the subnet level, not the VM level. When a route table is associated with a subnet, Azure inserts the user-defined routes into the effective routes for all network interfaces in that subnet. The next hop type 'Virtual appliance' requires IP forwarding to be enabled on the appliance's NIC; without subnet association, the VM's traffic never reaches the appliance's IP. In real-world scenarios, forgetting to associate the route table is a common misconfiguration that leads to traffic still using the default gateway (0.0.0.0/0).
KKey Concepts to Remember
- User-Defined Routes (UDRs) override Azure's default system routes.
- A route table must be explicitly associated with a subnet to apply its UDRs.
- Each subnet can only be associated with one route table.
- If no route table is associated, Azure's default routing rules apply.
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
User-Defined Routes (UDRs) override Azure's default system routes.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review user-Defined Routes (UDRs) override Azure's default system routes., then practise related AZ-104 questions on the same topic to reinforce the concept.
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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 — User-Defined Routes (UDRs) override Azure's default system routes..
What is the correct answer to this question?
The correct answer is: Whether the route table is associated with the correct subnet. — The most common reason a UDR fails to take effect is that the route table is not associated with the subnet containing the VM. Even if the route table contents are correct, the VM's traffic will follow default system routes unless the route table is explicitly linked to the subnet. Association is a required step to override Azure's default routing behavior.
What should I do if I get this AZ-104 question wrong?
Review user-Defined Routes (UDRs) override Azure's default system routes., then practise related AZ-104 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
User-Defined Routes (UDRs) override Azure's default system routes.
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Last reviewed: Jun 11, 2026
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