Azure Load Balancer Tutorial: Complete Guide for Beginners

Introduction to Azure Load Balancer

Azure Load Balancer is one of the most important networking services in Microsoft Azure that helps your applications improve availability, scalability, and performance. If you are a student, fresher, working professional, or preparing for Azure certifications such as AZ-900, AZ-104, or AZ-305, you have to understand that Azure Load Balancer is an essential skill for cloud computing.

In modern real-time projects, applications are usually deployed across multiple Virtual Machines (VMs). If all the user traffic is sent to only one server, it can become overloaded or unavailable during failures. Azure Load Balancer will resolve this problem by securely distributing incoming traffic across multiple healthy resources such as Virtual Machines and databases, ensuring that your application remains available and performs efficiently.

In this step-by-step Guide, you will learn:

1. What is Azure Load Balancer
2. Why do we use Azure Load Balancer
3. Types of Azure Load Balancer.
4. Frontend IP Configuration.
5. Backend Address Pools
6. Hands-on Azure Load Balancer Configuration.
7. Real-time Use Cases and Best Practices.

1. What is Azure Load Balancer

Azure Load Balancer is a load-balancing service in Azure that distributes incoming web traffic or user traffic across multiple resources such as Virtual Machines, Databases, etc.

2. Why do we use Azure Load Balancer

To maintain high availability, Scalability, and automatic failover of your application. Instead of directly allowing thousands of users to connect to a single server, it securely distributes requests among multiple healthy servers, improving availability, performance, and reliability.

3. Types of Azure Load Balancer

There are 2 types of Azure Load Balancers: Public Load Balancer and Internal or Private Load Balancer. Public Load Balancer is used to route Internet user traffic across multiple web servers based on health probes and the availability of Web servers.

4. Frontend IP configuration

Frontend IP Configuration in Azure Load Balancer is the 1st entry point through which the Load Balancer receives incoming network traffic from users or applications. It defines the IP address (public or private) that clients use to access your application. Every Public load balancer has a unique ip addresse which user directly access for the application.

5. Backend Address Pools

A Backend Address Pool is the group of multiple servers (such as Azure Virtual Machines) that actually handle user requests. The Azure Load Balancer will distribute traffic among these resources and automatically route traffic only to healthy instances or servers, ensuring high availability and reliable application performance.

Before configuring Azure Load Balancer, I would suggest doing the following steps.

Create 2 Virtual Machines with the Same Configuration

I have created 2 identical Windows Servers; please go with a basic configuration (B1 series). If the basic configuration is not available for your Azure subscription, please go with the configuration as shown in the snapshot.

Note: Please allow Port Numbers (HTTP 80, RDP 3389)

While creating Virtual Machine VM1, please create a Load Balancer in the Networking step with the configuration below, as shown in the snapshots.

Once you have created VM1 along with the Load Balancer, please create Virtual Machine 2 with the same configuration (Same Virtual Network, Same Subnet as Virtual Machine 1). 

Note: We are using the same VNET and SUBNET for Both Virtual Machines.

After you have created 2 Windows Virtual Machines, please log into both servers and install the Web Server (IIS) in both Virtual Machines in Windows Server Manager. Please refer to the snapshot below for your understanding. Also, Server Manager → Add Roles and Features → Role-based or Feature-based Installation → Select the Virtual Machine → Select Web Server (IIS) → Click Next on each screen until the Install page appears → Click Install

Once you have successfully installed, please check whether you are able to access the Web Server IIS Page in the browser as shown in the snapshot below.

Type: http://localhost in Edge or Google Chrome. After that, you will see the webpage below

For getting better understanding of how an Azure Load Balancer distributes traffic between multiple Virtual Machines, it is recommended to customise the default IIS web page on both Virtual Machines so that each displays different content. This will help you identify which Virtual Machine is serving the request during testing.

Follow this path: File Explorer → C:\inetpub\wwwroot → iisstart.htm → Right-click and select Open with → Notepad

For Virtual Machine VM1, this is my webpage content

For Virtual Machine VM2, this is my webpage content

Real-time Testing of Azure Load Balancer

Now, we have completed all the required configurations and steps, and now it's time to test Azure Load Balancer in real time.

Copy the Frontend IP Address of your Azure Load Balancer, which is mapped to both Veerpedia-VM1 and Veerpedia-VM2. This IP address will receive incoming requests from users through the internet and securely distribute the traffic between the backend Virtual Machines.

You can find the Frontend IP Address by following the path below:

Azure Load Balancer → Overview → Scroll down to "Balanced IPv4 and IPv6 Addresses" → Click "View Frontend IP Configuration"

Once you have copied the Frontend IP Address, paste it into your web browser (Edge or Google Chrome) and press Enter. Refresh the webpage multiple times (you can use Ctrl + F5 for a hard refresh). If the Azure Load Balancer has been configured successfully, you will observe that the requests are being routed alternately by Veerpedia-VM1 and Veerpedia-VM2. 

As we have already customised the IIS default web page on both Virtual Machines, the webpage content displayed in the browser will help you identify which Virtual Machine is currently serving the request. This provides a clear understanding of how Azure Load Balancer distributes traffic across multiple healthy backend resources.

If you want a step-by-step demo, please watch the YouTube Tutorial.