AZ-500 Secure networking Practice Question
Your company uses Azure Firewall to protect a virtual network. The security team needs to allow outbound HTTPS traffic from a specific subnet to a set of FQDNs, such as '*.contoso.com', while blocking all other outbound traffic. Which type of Azure Firewall rule should they configure?
⚠ Common exam trap
Many exam-takers confuse network rules (which filter by IP/port) with application rules (which filter by FQDN), leading them to choose Option A because they think resolved IPs are sufficient, ignoring the dynamic nature of FQDNs and the need for domain-level control.
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
✓
An application rule with the 'Https' protocol and the target FQDNs set to '*.contoso.com'
Azure Firewall application rules are specifically designed to allow outbound HTTP/HTTPS traffic based on fully qualified domain names (FQDNs). By configuring an application rule with protocol 'Https' and target FQDNs set to '*.contoso.com', the firewall inspects the TLS Server Name Indication (SNI) extension to match the requested domain, allowing traffic only to the specified FQDNs while blocking all other outbound traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A network rule with destination port 443 and protocol TCP, and the destination IP address set to the resolved IPs of the FQDNs
Why it's wrong here
A network rule in Azure Firewall operates at Layers 3/4 and can only match the destination IP address, protocol, and port—it never inspects the SNI hostname or HTTP Host header. Setting the destination to a manually resolved IP list for *.contoso.com would require you to constantly track and update DNS changes, so any IP rotation from a CDN or load balancer would silently break the rule or overpermit if you use a wide range. This makes it an impractical and fragile solution compared to an application rule that natively evaluates FQDNs.
- ✓
An application rule with the 'Https' protocol and the target FQDNs set to '*.contoso.com'
Why this is correct
Application rules are designed to allow or deny outbound traffic based on FQDNs. For HTTPS traffic, you can specify the target FQDNs and the protocol (Https). This is the correct configuration to allow traffic to specific domains while blocking others.
- ✗
A NAT rule that translates the source IP to a public IP and allows traffic to any destination on port 443
Why it's wrong here
A NAT or DNAT rule in Azure Firewall is designed to translate inbound destination IP/port information for traffic arriving at the firewall; it cannot be used to rewrite the source IP of outbound traffic or to enforce outbound destination filtering. Even if such a rule were possible, allowing any destination on port 443 with a source translation would permit every HTTPS website, including non-contoso.com destinations, completely failing the requirement to allow only specific domains. Outbound source NAT is automatically applied by the firewall, not governed by a user-defined NAT rule.
- ✗
A DNAT rule that redirects outbound HTTPS traffic to an internal proxy server
Why it's wrong here
DNAT rules are exclusively for inbound traffic—they alter the destination IP and port of packets before being forwarded to a backend resource—and they cannot redirect outbound flow from a workload to an internal proxy. Redirecting outbound HTTPS to a proxy would require explicit User-Defined Routes or a transparent proxy configuration, not a DNAT rule; additionally, this approach would still not restrict traffic to contoso.com unless the proxy itself is configured with filtering rules. Since the question asks for a firewall rule that directly allows specific FQDNs, this option is invalid.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-500 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-500 exam.