Quick Answer
The answer is that an NSG blocking inbound TCP 443 is the most likely Azure-side cause. This is correct because Network Security Groups act as a distributed firewall at the Azure network layer, filtering traffic before it ever reaches the VM’s guest OS. Even if the VM has a public IP and the application is listening on port 443, an NSG rule denying inbound HTTPS traffic will silently drop packets from the internet, making the application unreachable regardless of the guest firewall settings. On the AZ-104 exam, this scenario tests your understanding of Azure network security layers and the common trap of assuming a public IP guarantees connectivity. Remember that NSGs evaluate inbound traffic first, so a deny rule for TCP 443 on the subnet or NIC will block all external HTTPS access. A helpful memory tip: “NSG first, OS second—if the NSG says no, the traffic doesn’t flow.”
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.
Users on the internet cannot reach an HTTPS application hosted on VM-Web01. The VM has a public IP address, the application is listening on TCP port 443, and the guest OS firewall allows the traffic. What is the most likely Azure-side cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The NSG blocks inbound TCP 443
A missing allow rule or an explicit deny rule in the NSG will block internet access to the web application.
The VM uses Premium SSD
Why wrong: The storage type does not control inbound HTTPS connectivity.
Azure Backup is not enabled
Why wrong: Backup configuration does not affect inbound web traffic.
The storage account uses GRS
Why wrong: Storage redundancy is unrelated to this VM connectivity issue.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The NSG blocks inbound TCP 443
The most likely Azure-side cause is that a Network Security Group (NSG) associated with the VM's subnet or NIC is blocking inbound TCP port 443. Even if the VM has a public IP, the application is listening, and the guest OS firewall allows traffic, an NSG rule denying inbound HTTPS traffic will prevent external users from reaching the application. NSGs act as a distributed firewall filtering traffic at the Azure network layer before it reaches the VM.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The NSG blocks inbound TCP 443
Why this is correct
A missing allow rule or an explicit deny rule in the NSG will block internet access to the web application.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
The VM uses Premium SSD
Why it's wrong here
The storage type does not control inbound HTTPS connectivity.
Azure Backup is not enabled
Why it's wrong here
Backup configuration does not affect inbound web traffic.
The storage account uses GRS
Why it's wrong here
Storage redundancy is unrelated to this VM connectivity issue.
Common exam traps
The trap here is that candidates often focus on the VM's guest OS firewall or public IP configuration, overlooking the NSG as the first line of defense in Azure's network security model.
Detailed technical explanation
NSGs contain security rules that are evaluated in priority order, with each rule specifying source, destination, port, and protocol. By default, NSGs have an implicit 'DenyAllInbound' rule at the lowest priority, so without an explicit 'Allow' rule for TCP 443, all inbound HTTPS traffic is blocked. This filtering occurs at the Azure host level, before the traffic reaches the VM's guest OS, making it invisible to the guest firewall.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
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FAQ
Implement and Manage Virtual Networking — This question tests Implement and Manage Virtual Networking — Read the scenario before looking for a memorised answer..
The correct answer is: The NSG blocks inbound TCP 443 — The most likely Azure-side cause is that a Network Security Group (NSG) associated with the VM's subnet or NIC is blocking inbound TCP port 443. Even if the VM has a public IP, the application is listening, and the guest OS firewall allows traffic, an NSG rule denying inbound HTTPS traffic will prevent external users from reaching the application. NSGs act as a distributed firewall filtering traffic at the Azure network layer before it reaches the VM.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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