The answer is to create an NSG rule allowing TCP 3389 from the Subnet-Mgmt address range and rely on the default deny afterward. This works because Network Security Groups (NSGs) evaluate rules in priority order, and every NSG includes a default implicit deny rule that blocks all inbound traffic not explicitly permitted. By adding a specific allow rule for RDP from your management subnet, you override that default deny only for that source, while all other sources remain blocked automatically. On the AZ-104 exam, this scenario tests your understanding of NSG rule evaluation and the critical concept that you do not need to create a separate deny rule—the implicit deny handles it. A common trap is thinking you must add an explicit deny rule for other subnets, which wastes priority slots and can introduce misconfiguration. Remember the memory tip: "Allow what you need, deny is already there"—the default deny is your silent partner, so just focus on writing precise allow rules.
AZ-104 Implement and Manage Virtual Networking Practice Question
This AZ-104 practice question tests your understanding of implement and manage virtual networking. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 subnet contains several application servers. You need to allow inbound TCP 3389 only from a management subnet named Subnet-Mgmt and deny RDP from all other sources. What should you do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create an NSG rule allowing TCP 3389 from the Subnet-Mgmt address range and rely on the default deny afterward.
Option A is correct because Network Security Groups (NSGs) in Azure filter traffic based on rules that are evaluated in priority order. By creating an inbound rule that allows TCP 3389 (RDP) from the Subnet-Mgmt address range, and relying on the default implicit deny rule that blocks all other inbound traffic, you effectively restrict RDP access to only the management subnet. No additional configuration is needed to deny traffic from other sources, as the default deny handles that automatically.
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.
✓
Create an NSG rule allowing TCP 3389 from the Subnet-Mgmt address range and rely on the default deny afterward.
Why this is correct
This is the correct way to permit RDP from a specific source while denying other sources.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a route table that sends RDP traffic to the management subnet.
Why it's wrong here
Route tables do not implement port-based access control.
✗
Deploy a private endpoint for each application server.
Why it's wrong here
Private endpoints are for Azure PaaS services, not exposing VM RDP selectively.
✗
Enable service endpoints on the application subnet.
Why it's wrong here
Service endpoints are unrelated to RDP access control.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think they need to explicitly create a deny rule for all other sources, not realizing that NSGs have a built-in default deny rule that automatically blocks traffic not matching any allow rule.
Detailed technical explanation
How to think about this question
NSG rules are stateful, meaning that if you allow inbound traffic, the return traffic is automatically allowed regardless of outbound rules. The default inbound rule 'DenyAllInBound' has a priority of 65000 and applies after all custom rules, so a custom rule with a higher priority (lower number) allowing RDP from Subnet-Mgmt will be evaluated first, and all other traffic will hit the default deny. In a real-world scenario, you might also need to consider using Azure Bastion as a more secure alternative to RDP, but the question specifically asks about NSG-based filtering.
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
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-104 question in full detail.
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: Create an NSG rule allowing TCP 3389 from the Subnet-Mgmt address range and rely on the default deny afterward. — Option A is correct because Network Security Groups (NSGs) in Azure filter traffic based on rules that are evaluated in priority order. By creating an inbound rule that allows TCP 3389 (RDP) from the Subnet-Mgmt address range, and relying on the default implicit deny rule that blocks all other inbound traffic, you effectively restrict RDP access to only the management subnet. No additional configuration is needed to deny traffic from other sources, as the default deny handles that automatically.
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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