Detailed guide on implementing Public Load Balancer in Azure

Implementing a Public Load Balancer in Azure involves several steps.

The Public Load Balancer distributes traffic from the internet to backend resources like Virtual Machines (VMs) within a Virtual Network (VNet).

Here's a step-by-step guide to implement it.

Plan Your Load Balancer Deployment

Before creating the load balancer, consider the following:

Frontend IP

This is the public IP that clients use to connect to the load balancer.

Backend Pool

A set of VMs or resources that will receive traffic.

Health Probes

Used to monitor the health of the backend resources.

Load Balancing Rules

Define how traffic is distributed among the backend resources.

Prerequisites

1. Azure Subscription

Ensure you have an active subscription.

2. Virtual Machines

Create two or more VMs in a VNet (if not already done).

3. Public IP Address

Decide whether to use an existing public IP or create a new one.

Steps to Create a Public Load Balancer

Step 1: Create a Public Load Balancer

1. Navigate to the Azure Portal.

2. In the search bar, type Load Balancers and select it.

3. Click + Create to create a new Load Balancer.

4. Fill out the basic details:

   • Subscription: Choose your Azure subscription.

   • Resource Group: Select an existing resource group or create a new one.

   • Region: Choose the region where the resources are deployed.

   • Name: Give the load balancer a meaningful name.

   • SKU: Choose Standard or Basic (Standard is recommended for production).

   • Type: Select Public.

   • Frontend IP Configuration: Create a new public IP or use an existing one.

5. Click Review + Create, then click Create to deploy the load balancer.

Step 2: Configure the Backend Pool

1. After the load balancer is created, go to its Overview page.

2. Click on Backend Pools under Settings.

3. Click + Add to create a backend pool.

4. Provide a name for the backend pool (e.g., WebAppBackend).

5. For Backend Pool Configuration, select:

   • Associated to: Virtual Machine.

   • Add Virtual Machines: Select the VMs to add to the pool.

6. Click Add to save the backend pool configuration.

Step 3: Create Health Probes

1. In the Load Balancer settings, click on Health Probes.

2. Click + Add to create a new health probe.

3. Fill out the required details:

   • Name: Give a descriptive name (e.g., WebAppHealthProbe).

   • Protocol: Select TCP, HTTP, or HTTPS.

   • Port: Specify the port to monitor (e.g., 80 for HTTP or 443 for HTTPS).

   • Interval: Set the frequency of health checks (default is 5 seconds).

   • Unhealthy Threshold: Define the number of consecutive failures to mark a backend as unhealthy.

4. Click OK to save the health probe.

Step 4: Configure Load Balancing Rules

1. In the Load Balancer settings, click on Load Balancing Rules.

2. Click + Add to create a new rule.

3. Configure the rule:

   • Name: Provide a descriptive name (e.g., WebAppRule).

   • Frontend IP Configuration: Select the public IP created earlier.

   • Protocol: Choose TCP.

   • Port: Specify the frontend port (e.g., 80 for HTTP).

   • Backend Port: Specify the backend port (e.g., 80).

   • Backend Pool: Select the backend pool created earlier.

   • Health Probe: Select the health probe created earlier.

   • Session Persistence: Choose a session persistence mode (e.g., None or Client IP).

   • Idle Timeout (minutes): Set the timeout duration (default is 4 minutes).

   • Floating IP: Leave this as Disabled for basic scenarios.

4. Click Add to save the rule.

Test the Public Load Balancer

1. Obtain the public IP address of the load balancer from the Frontend IP Configuration section.

2. Open a web browser and enter the public IP address.

3. The request should be routed to one of the backend VMs.

4. Test high availability by stopping one VM and confirming that the load balancer directs traffic to the remaining healthy VM(s).

Optional Configuration

Configure Outbound Rules

If you need backend VMs to initiate outbound traffic using the load balancer's public IP, configure outbound rules in the load balancer settings.

Network Security Groups (NSGs)

Ensure the NSG on your VMs or subnet allows inbound traffic on the required ports (e.g., HTTP: 80 or HTTPS: 443).

Autoscaling

Integrate with Virtual Machine Scale Sets for dynamic scaling of backend instances.

Key Considerations

1. Choose Standard SKU for production workloads due to its enhanced security, availability zone support, and scalability.

2. NSG Rules: Ensure the backend VMs are accessible only through the load balancer to enhance security.

3. Diagnostics: Enable monitoring through Azure Monitor for performance insights and health diagnostics.

Summary

By following these steps, you can effectively implement a Public Load Balancer in Azure to ensure high availability and scalability for your applications.