How to Set Up Azure Load Balancer for High Availability

When you build apps or services in the cloud, keeping them available is always a top priority. Azure Load Balancer is a tool that can help you do this by spreading traffic across multiple resources. 

In this guide, I’ll walk you step by step through how to set it up. You’ll learn everything from planning your configuration to testing and monitoring your Load Balancer.

Azure Load Balancer Basics  

Before we start, let’s quickly look at what Azure Load Balancer does.

Azure Load Balancer is a network service that distributes incoming and outgoing traffic across healthy virtual machines. It works at the transport layer and supports both public and private access.

Key components you’ll see as you set things up include:

• Frontend IP configuration, which is the address clients connect to.
  
• Backend pool, a group of servers handling the requests.
  
• Health probes, which check if your servers are working.
  
• Load balancing rules, decide how traffic moves.
  
• Outbound rules, control outbound connections.
  

If you’d like a deeper explanation of these terms, you can read my first guide, Understanding Azure Load Balancer, before you continue.

Prerequisites

Before you start, make sure you have:

• An Azure subscription where you can create resources.
  
• At least two virtual machines or services to use as your backend pool.
  
• A resource group to organize your Load Balancer and related resources.
  
• A virtual network where your backend servers live.
  
• Basic familiarity with the Azure portal or Azure CLI.
  

Planning Your Configuration

Taking a little time to plan will save you headaches later. Here are the decisions you need to make:

• SKU Selection: Choose Standard SKU if you need production-grade features, more security, and higher scaling. Use Basic SKU only for simple or test workloads.
  
• Type of Load Balancer: Decide if you need a Public Load Balancer (for internet-facing apps) or an Internal Load Balancer (for private apps within your network).
  
• Frontend IP: Plan whether it will be a public or private IP address.
  
• Backend Resources: Identify which virtual machines or scale sets will handle the traffic.
  

Creating the Load Balancer

Here’s how you create the Load Balancer in the Azure Portal:

1. Sign in to the Azure portal.
   
2. In the left menu, select Create a resource.
   
3. Search for Load Balancer and click Create.

4. Fill in the basic details:
   
   • Subscription
     
   • Resource group
     
   • Name of your Load Balancer
     
   • Region
     
   • SKU (Standard or Basic)
     
   • Type (Public or Internal)
     
5. For a Public Load Balancer, create or select a Public IP Address.
   
6. Click Review + create, then Create.
   

Optional: If you prefer, you can also use Azure CLI or PowerShell to create the Load Balancer.

Setting Up the Frontend IP

After creation, you need to configure the frontend IP address:

1. In your Load Balancer resource, select Frontend IP configuration.
   
2. Click + Add.
   
3. Enter a name for this configuration.

4. Choose Public IP (for internet access) or Private IP (for internal access).
   
5. If using a public IP, you can assign a DNS name label for easier access.
   
6. Click Save and move to the next configuration.
   

Defining the Backend Pool

Next, create your backend pool:

1. Go to Backend pools in the Load Balancer settings.
   
2. Click + Add a backend pool.

3. Give it a name.
   
4. Choose the Virtual Network where your backend servers are located.
   
5. Select the virtual machines or virtual machine scale sets to include in the pool.
   
6. Click Save.

7. Click the Next: Inbound Rules button.

This group of resources will receive traffic from the Load Balancer.

Creating Load Balancing Rules

Load balancing rules define how traffic moves between frontend and backend:

1. Go to Load balancing rules in your Load Balancer.
   
2. Click + Add.
   
3. Configure these settings:
   
   • Name
     
   • Frontend IP configuration to use
     
   • Backend pool
     
4. In the Load Balancer settings, select Health probes.
   
5. Click + Create New.
   
6. Fill in the details:
   
   • Name
     
   • Protocol (TCP, HTTP, or HTTPS)
     
   • Port to probe 

• Interval and unhealthy threshold
  

7. Click OK.
   
   • Protocol (TCP or UDP)
     
   • Port (for example, 80 for HTTP)
     
   • Backend port
     
   • Session persistence (None, Client IP, or Client IP and protocol)
     
   • Idle timeout
     
   • Enable or disable Floating IP (usually off for most scenarios)
     
8. Click Save.
   

Adding Outbound Rules (If Needed)

Outbound rules control how backend servers make outbound connections to the internet:

1. In the Load Balancer menu, select Outbound rules.
   
2. Click + Add.
   
3. Choose the frontend IP configuration.
   
4. Assign the backend pool.
   
5. Set protocol and ports as needed.
   
6. Click OK.
   

If your backend VMs need to make outbound connections, this ensures they share the same public IP.

At the end, click Create to end the process. 

Testing Your Configuration

Once you finish setup, it’s important to test:

• Click Go to resource to open your Azure Load Balancer

• Verify backend health in the Azure portal.
  
• Connect to the frontend IP and confirm traffic reaches your servers.
  
• Shut down one backend VM and verify if traffic automatically reroutes to the healthy VMs.
  
• Check monitoring logs for probe results and traffic statistics.
  

Testing now helps avoid surprises later.

Monitoring and Troubleshooting

Keep your Load Balancer healthy by:

• Using Azure Monitor to track metrics like data throughput and backend health.

• Setting alerts for unusual activity or failed probes.
  
• Reviewing logs in Azure Network Watcher to see if something isn’t working.
  
• Double-checking firewall rules, NSGs, and routing if traffic isn’t flowing as expected.
  

Best Practices and Tips

Here are a few simple tips to get the most out of your setup:

• Use zone redundancy in Standard SKU to avoid downtime if an availability zone fails.
  
• Plan for scaling by designing your backend pool to handle peak traffic.
  
• Secure endpoints with proper NSG rules and limit public access when possible.
  
• Regularly test failover to confirm your configuration works as planned.
  

Conclusion

I hope this guide has made it clear how to set up Azure Load Balancer step by step. By taking time to plan, test, and monitor, you can build a reliable foundation for your apps. If you’d like help fine-tuning your setup or exploring more Azure services, feel free to reach out or check out other guides.