The correct answer is to enable DNS proxy on the firewall policy. This feature allows Azure Firewall to listen on port 53 and act as an intermediary, forwarding DNS queries from virtual machines in the spoke VNet to the configured custom DNS server, thereby ensuring all DNS traffic is logged and inspected. Simply setting a custom DNS server on the firewall is insufficient because the VMs themselves must be configured to use the firewall’s private IP address as their DNS server; the DNS proxy handles the forwarding and logging at the firewall level. On the AZ-500 exam, this scenario tests your understanding of how to enforce DNS inspection in a hub-and-spoke topology, and a common trap is assuming that a custom DNS server alone forces traffic through the firewall—without the proxy, VMs may bypass it. Memory tip: think “DNS proxy = port 53 forwarder” to remember it bridges the VMs to the custom DNS server while keeping all queries under firewall inspection.
AZ-500 Secure networking Practice Question
This AZ-500 practice question tests your understanding of secure 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 company uses Azure Firewall to filter outbound traffic. They want to ensure that all DNS queries from virtual machines in a spoke VNet are routed through the Azure Firewall for logging and inspection. They have already configured the firewall to use a custom DNS server. Which additional Azure Firewall feature must be enabled to ensure that the VMs use the firewall as a DNS proxy?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable DNS proxy on the firewall policy
Option A is correct because enabling DNS proxy on the Azure Firewall policy allows the firewall to act as a DNS proxy for the virtual machines in the spoke VNet. When DNS proxy is enabled, the firewall listens on port 53 and forwards DNS queries from the VMs to the configured custom DNS server, ensuring all DNS traffic is logged and inspected. This is required even after setting a custom DNS server on the firewall, as the VMs must be configured to use the firewall's private IP address as their DNS server, and the proxy handles the forwarding.
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.
✓
Enable DNS proxy on the firewall policy
Why this is correct
Correct. DNS proxy enables the firewall to act as a DNS proxy, accepting DNS queries from VMs and forwarding them to the configured DNS server.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure a DNS forwarding rule
Why it's wrong here
Incorrect. Azure Firewall does not have a DNS forwarding rule; DNS proxy is the feature that handles DNS traffic forwarding.
✗
Enable Threat Intelligence DNS logging
Why it's wrong here
Incorrect. This feature logs DNS queries based on threat intelligence but does not route DNS traffic through the firewall.
✗
Create a NAT rule for DNS traffic
Why it's wrong here
Incorrect. NAT rules are used to translate destination IP addresses/ports, not to proxy DNS queries.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse enabling DNS proxy with simply configuring a custom DNS server on the firewall, or they think that a NAT rule or forwarding rule alone will route DNS traffic through the firewall, but without the DNS proxy feature, the firewall does not listen on port 53 and cannot intercept DNS queries from VMs.
Detailed technical explanation
How to think about this question
Under the hood, when DNS proxy is enabled on Azure Firewall, the firewall listens on UDP and TCP port 53 on its private IP address. The VMs in the spoke VNet must have their DNS server settings configured to point to the firewall's private IP (e.g., via DHCP or custom DNS settings on the VNet). The firewall then forwards the DNS queries to the custom DNS server specified in the firewall policy, and all responses are cached and returned to the VMs. This ensures that all DNS traffic is logged and can be inspected by Azure Firewall's threat intelligence and application rules. In a real-world scenario, this is critical for enforcing DNS security policies, such as blocking known malicious domains, and for auditing all DNS queries from workloads.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-500 question in full detail.
Secure networking — This question tests Secure networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable DNS proxy on the firewall policy — Option A is correct because enabling DNS proxy on the Azure Firewall policy allows the firewall to act as a DNS proxy for the virtual machines in the spoke VNet. When DNS proxy is enabled, the firewall listens on port 53 and forwards DNS queries from the VMs to the configured custom DNS server, ensuring all DNS traffic is logged and inspected. This is required even after setting a custom DNS server on the firewall, as the VMs must be configured to use the firewall's private IP address as their DNS server, and the proxy handles the forwarding.
What should I do if I get this AZ-500 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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Question Discussion
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