Use Application Load Balancers for Web Servers

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Use Application Load Balancers for Web Servers

Load balancing automatically distributes your incoming traffic across multiple targets, such as EC2 instances, containers, and IP addresses, in one or more Availability Zones. In this lab, we configure an Application Load Balancer to distribute network traffic to two EC2 instances. We then enable stickiness, so that once a server is contacted, the user is always sent to that server. This ensures our legacy application continues to work despite not supporting distributed logins. By the end of this lab, the user will understand how to create an Application Load Balancer and enable sticky sessions.

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Lab Info

Level

Beginner

Last updated

Sep 24, 2025

Duration

1h 0m

Challenge

Observe the Provided EC2 Website and Create a Second Server

NOTE: While we generally recommend folloiwng the steps in the lab as shown, if you have trouble with using any of the public IPs referrenced in the lab, you can try using the public DNS name instead (Please be aware that DNS propogation delays are possible with this approach).

Observe the website configured on the existing EC2 server. Using the bootstrap script provided, boot another EC2 server.

For your new EC2 use the following settings:

For your AMI, use Ubuntu Server 22.04 LTS.

Note: If you get a popup window that tells you some of your current settings will be changed, click on Confirm changes.
Under Network settings, enable the option to Auto-assign Public IP.
For the security groups, select the one with EC2SecurityGroup in its name (not the default security group).
Add the following bootstrap script:

    #!/bin/bash
    
    # Update and install necessary packages
    sudo apt-get update -y
    sudo apt-get install -y apache2 unzip
    
    # Fetching the token for IMDSv2
    TOKEN=`curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600"`
    
    # Starting HTML file
    echo '<html><center><body bgcolor="black" text="#39ff14" style="font-family: Arial"><h1>Load Balancer Demo</h1><h3>Availability Zone: ' > /var/www/html/index.html
    
    # Using the token to fetch metadata
    echo $(curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/placement/availability-zone) >> /var/www/html/index.html
    echo '</h3> <h3>Instance Id: ' >> /var/www/html/index.html
    echo $(curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/instance-id) >> /var/www/html/index.html
    echo '</h3> <h3>Public IP: ' >> /var/www/html/index.html
    echo $(curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/public-ipv4) >> /var/www/html/index.html
    echo '</h3> <h3>Local IP: ' >> /var/www/html/index.html
    echo $(curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/local-ipv4) >> /var/www/html/index.html
    
    # Ending HTML file
    echo '</h3></html> ' >> /var/www/html/index.html
    
    # - Ensure the Apache2 service is enabled and started.
    sudo systemctl enable apache2
    sudo systemctl start apache2

Challenge

Create an Application Load Balancer

Create a load balancer called LegacyALB with a target group called TargetGroup, add the two EC2 servers as targets, and observe how the load balancing works in your web browser.
Challenge

Enable Sticky Sessions

Configure the load balancer to use stickiness, and observe how the load balancer now only directs the user to a single EC2 server (as expected).

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