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How to Create an Application Load Balancer (ALB) in AWS: A Step-by-Step Guide

In today’s cloud infrastructure, efficiently distributing incoming traffic is crucial to ensure high availability and fault tolerance. AWS’s Application Load Balancer (ALB) is a powerful solution designed to handle such traffic distribution, particularly for applications with complex routing needs. In this tutorial, we’ll guide you through the process of creating an ALB from scratch.

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What is an Application Load Balancer (ALB)?
An Application Load Balancer operates at the OSI model’s application layer (Layer 7). It routes traffic based on content within the request, such as URLs, headers, and query strings. This makes it ideal for microservices architectures and containerized applications.

Key features of ALB include:

Content-based routing: Routes requests to specific services based on content in the request.
SSL termination: Offloads the SSL/TLS encryption/decryption to the ALB, saving compute resources on backend instances.
Monitoring and logging: Integrated with CloudWatch for performance metrics and access logs.
Dynamic scaling: Automatically scales to handle varying levels of traffic.

For a visual walkthrough of the concepts covered in this article, check out my YouTube Video:-
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Prerequisites
Before getting started, ensure you have:

An AWS account.
EC2 instances or target services to attach to the load balancer.
Step-by-Step Guide to Create an Application Load Balancer

Step 1: Access the Load Balancer Section

  • Log in to your AWS Management Console.
  • Navigate to the EC2 Dashboard.
  • On the left-hand menu, under Load Balancing, click Load Balancers. Step 2: Create a New Load Balancer
  1. Click the Create Load Balancer button.
  2. Choose Application Load Balancer as the type.
  3. Specify the following:
  • Name: Enter a name for the ALB.
  • Scheme: Choose either Internet-facing (for public access) or Internal (for private access).
  • IP Address Type: Select either IPv4 or Dualstack (if supporting both IPv4 and IPv6).

Step 3: Configure Listeners and Availability Zones

  1. Listeners: Define the listener, which is the port the ALB will use to receive traffic (HTTP or HTTPS). For HTTPS, you’ll need to set up an SSL certificate.
  2. Availability Zones: Select at least two Availability Zones (AZs) for high availability. Assign a subnet from each AZ.

Step 4: Configure Security Settings (for HTTPS)
If you are setting up HTTPS, choose an SSL certificate from AWS Certificate Manager (ACM) or upload your own.

Step 5: Configure Target Groups

1.Create a target group to which the ALB will route traffic.

  • Choose the target type: instances, IP addresses, or Lambda functions.
  • Set the health check path to monitor the targets’ health (e.g., /health). 2.Register your EC2 instances or targets.

Step 6: Configure Security Groups

  1. Assign a security group to the ALB that allows incoming traffic on the listener port (e.g., port 80 for HTTP).
  2. Ensure that the backend instances’ security groups allow traffic from the ALB.

Step 7: Review and Create
Review your configuration, ensuring all settings are correct. Click Create to launch your ALB.

Step 8: Test Your Application Load Balancer
Once your ALB is active, it will display a DNS name. Use this DNS name to test that traffic is properly routed to your targets.

Conclusion
Creating an AWS Application Load Balancer is a straightforward process that significantly enhances your application’s scalability and availability. By following this guide, you can ensure your cloud infrastructure is optimized for high traffic loads and maintain smooth operations even during peak times.

With features like intelligent routing, health checks, and SSL termination, the ALB is an essential tool for any modern application architecture.

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