AZ-305 Design infrastructure solutions Practice Question
A company is planning to migrate a legacy application to Azure VMs. The application requires a static IP address for licensing purposes. The VM must be highly available within a single region. Which combination of Azure resources should they use?
⚠ Common exam trap
Many exam-takers confuse availability zones with availability sets, assuming zones provide better HA, but for a single-region legacy app with a static IP, an availability set is the correct choice because it offers fault domain redundancy without the complexity of multi-zone deployment.
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
✓
Standard Load Balancer with a static frontend IP and availability set
A Standard Load Balancer with a static frontend IP provides a fixed IP address for licensing, and an availability set ensures high availability by distributing VMs across fault and update domains within a single region. This combination meets the requirement for a static IP and regional HA without needing scale-out or global routing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Application Gateway with a static frontend IP and virtual machine scale set
Why it's wrong here
Azure Application Gateway operates at Layer 7 (HTTP/HTTPS) and is designed for web traffic routing with features like URL path-based routing, TLS termination, and a Web Application Firewall. A legacy application that communicates over arbitrary TCP or UDP ports cannot be load-balanced by this service, since it inspects only HTTP(S) payloads. Furthermore, the proposal pairs it with a virtual machine scale set rather than an availability set, so it fails to address the fault-domain and update-domain redundancy expected for high availability.
- ✓
Standard Load Balancer with a static frontend IP and availability set
Why this is correct
The Standard Load Balancer is a Layer-4 (TCP/UDP) service that supports a static frontend IP address and can route traffic to a backend pool of VMs deployed within an availability set. An availability set spreads virtual machines across multiple fault domains and update domains, ensuring that a hardware failure or planned maintenance does not take down all instances at once. This configuration directly matches common legacy migration requirements: a fixed IP for client whitelisting and resilient handling of raw TCP/UDP sessions.
- ✗
Basic Load Balancer with a static frontend IP and availability zone
Why it's wrong here
The Basic Load Balancer SKU lacks support for availability zones; zone-redundant deployment requires the Standard SKU, which can explicitly pin or distribute frontend IPs across zones. Even if the backend VMs were placed in different availability zones, the Basic SKU would not honor zone-based fault isolation, so it cannot provide the promised high availability. Also, Basic SKU has no SLA, making it an inadequate choice for production workloads undergoing migration.
- ✗
Azure Front Door with a static backend IP and VM in an availability zone
Why it's wrong here
Azure Front Door is a global, application-layer (HTTP/HTTPS) entry point that routes traffic across regions based on hostnames and path rules, not a regional TCP/UDP load balancer for legacy applications. It requires public HTTP(S) endpoints and does not expose a static private frontend IP for low-level protocol traffic. The proposal also places the backend in a single availability zone, which provides no redundancy if that entire zone fails, and it omits an availability set for fault/update domain isolation.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-305 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-305 exam.