The correct answer is that the Azure Firewall does not have an allow rule for outbound internet traffic. This is because Azure Firewall operates on a default-deny model, meaning all traffic is blocked unless explicitly permitted by a network rule or application rule. Even though a DNAT rule exists, DNAT rules are used for inbound traffic translation, not for authorizing outbound connections; outbound traffic requires a dedicated allow rule in the firewall’s policy. On the Microsoft Azure Security Engineer Associate AZ-500 exam, this scenario tests your understanding of Azure Firewall rule evaluation order and the common misconception that a DNAT rule implies outbound permission. A frequent trap is assuming that a route pointing to the firewall or a permissive NSG is sufficient, but the firewall itself must explicitly allow the traffic. Memory tip: think of Azure Firewall as a bouncer—it blocks everyone at the door until you hand it a specific “allow” list for outbound passes.
AZ-500 Secure networking Practice Question
This AZ-500 practice question tests your understanding of secure 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.
You are troubleshooting an Azure virtual machine that cannot access the internet. The VM is in a subnet with a route table that has a default route (0.0.0.0/0) with next hop 'Virtual appliance' pointing to the private IP of an Azure Firewall. The Azure Firewall has a DNAT rule to allow outbound traffic. You verify that the VM's NSG allows outbound traffic. What is the most likely cause of the issue?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Azure Firewall does not have an allow rule for outbound internet traffic.
Option A is correct because Azure Firewall must have the 'Allow traffic' property set to allow outbound traffic. By default, Azure Firewall blocks all traffic unless an allow rule is configured. Option B is wrong because the VM's NSG allows outbound traffic. Option C is wrong because the route table exists and points to the firewall. Option D is wrong because Azure Firewall SNATs outbound traffic by default.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Azure Firewall does not support SNAT for outbound traffic.
Why it's wrong here
Azure Firewall supports SNAT for outbound traffic.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Scenario analysis trap
The scenario states NSG allows outbound traffic.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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-500 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related AZ-500 subnetting questions on CIDR, address ranges, and subnet selection.
Secure networking — This question tests Secure networking — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The Azure Firewall does not have an allow rule for outbound internet traffic. — Option A is correct because Azure Firewall must have the 'Allow traffic' property set to allow outbound traffic. By default, Azure Firewall blocks all traffic unless an allow rule is configured. Option B is wrong because the VM's NSG allows outbound traffic. Option C is wrong because the route table exists and points to the firewall. Option D is wrong because Azure Firewall SNATs outbound traffic by default.
What should I do if I get this AZ-500 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related AZ-500 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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