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Create an Application Load Balancer with Elastic Load Balancing

Overview

In this tutorial, you use the AWS CLI to create an Application Load Balancer (ALB) in your default VPC. You create a security group, target group, and HTTP listener, then verify the ALB is active. You then delete all resources during cleanup.

Prerequisites

  • AWS CLI installed and configured with appropriate permissions.
  • A default VPC with at least two subnets in different Availability Zones.
  • An IAM principal with permissions for elbv2:CreateLoadBalancer, elbv2:CreateTargetGroup, elbv2:CreateListener, elbv2:DescribeLoadBalancers, elbv2:DeleteLoadBalancer, elbv2:DeleteTargetGroup, elbv2:DeleteListener, ec2:CreateSecurityGroup, ec2:AuthorizeSecurityGroupIngress, ec2:DeleteSecurityGroup, ec2:DescribeVpcs, and ec2:DescribeSubnets.

Step 1: Get VPC and subnets

Identify the default VPC and select two subnets for the ALB. An ALB requires subnets in at least two Availability Zones.

VPC_ID=$(aws ec2 describe-vpcs --filters "Name=isDefault,Values=true" \
    --query 'Vpcs[0].VpcId' --output text)

SUBNETS=$(aws ec2 describe-subnets --filters "Name=vpc-id,Values=$VPC_ID" \
    --query 'Subnets[:2].SubnetId' --output text)
SUBNET1=$(echo "$SUBNETS" | awk '{print $1}')
SUBNET2=$(echo "$SUBNETS" | awk '{print $2}')
echo "VPC: $VPC_ID  Subnets: $SUBNET1, $SUBNET2"

Step 2: Create a security group

Create a security group that allows inbound HTTP traffic on port 80.

RANDOM_ID=$(openssl rand -hex 4)

SG_ID=$(aws ec2 create-security-group --group-name "tut-alb-sg-${RANDOM_ID}" \
    --description "Tutorial ALB security group" --vpc-id "$VPC_ID" \
    --query 'GroupId' --output text)

aws ec2 authorize-security-group-ingress --group-id "$SG_ID" \
    --protocol tcp --port 80 --cidr 0.0.0.0/0 > /dev/null
echo "Security group: $SG_ID"

This rule allows HTTP traffic from any source. In production, restrict the CIDR to known IP ranges.

Step 3: Create a target group

Create an IP-based target group. The ALB forwards traffic to targets registered in this group.

TG_NAME="tut-tg-${RANDOM_ID}"

TG_ARN=$(aws elbv2 create-target-group --name "$TG_NAME" \
    --protocol HTTP --port 80 --vpc-id "$VPC_ID" \
    --target-type ip \
    --query 'TargetGroups[0].TargetGroupArn' --output text)
echo "Target group: $TG_ARN"

Target type ip lets you register IP addresses directly. Use instance to register EC2 instances by ID instead.

Step 4: Create the Application Load Balancer

Create the ALB across the two subnets with the security group attached.

ALB_NAME="tut-alb-${RANDOM_ID}"

ALB_ARN=$(aws elbv2 create-load-balancer --name "$ALB_NAME" \
    --subnets $SUBNET1 $SUBNET2 \
    --security-groups "$SG_ID" \
    --query 'LoadBalancers[0].LoadBalancerArn' --output text)
echo "ALB ARN: $ALB_ARN"

Step 5: Wait for ALB to be active

The ALB takes 1–2 minutes to provision. Wait for it to reach the active state.

aws elbv2 wait load-balancer-available --load-balancer-arns "$ALB_ARN"

DNS_NAME=$(aws elbv2 describe-load-balancers --load-balancer-arns "$ALB_ARN" \
    --query 'LoadBalancers[0].DNSName' --output text)
echo "DNS: $DNS_NAME"

The DNS name is publicly resolvable. Without registered targets, requests to this DNS return a 503 error.

Step 6: Create an HTTP listener

Create a listener on port 80 that forwards traffic to the target group.

LISTENER_ARN=$(aws elbv2 create-listener --load-balancer-arn "$ALB_ARN" \
    --protocol HTTP --port 80 \
    --default-actions "Type=forward,TargetGroupArn=$TG_ARN" \
    --query 'Listeners[0].ListenerArn' --output text)
echo "Listener: $LISTENER_ARN"

The default action forwards all requests to the target group. You can add rules to route requests based on path or host header.

Step 7: Describe the ALB

View the ALB configuration.

aws elbv2 describe-load-balancers --load-balancer-arns "$ALB_ARN" \
    --query 'LoadBalancers[0].{Name:LoadBalancerName,DNS:DNSName,State:State.Code,Type:Type}' \
    --output table

Cleanup

Delete resources in reverse order. The ALB must be fully deleted before you can remove the target group.

aws elbv2 delete-listener --listener-arn "$LISTENER_ARN"
aws elbv2 delete-load-balancer --load-balancer-arn "$ALB_ARN"

echo "Waiting for ALB deletion..."
aws elbv2 wait load-balancers-deleted --load-balancer-arns "$ALB_ARN"

aws elbv2 delete-target-group --target-group-arn "$TG_ARN"
aws ec2 delete-security-group --group-id "$SG_ID"

ALBs incur hourly charges (~$0.02/hr) plus data processing fees. Clean up promptly to avoid costs.

The script automates all steps including cleanup:

bash elastic-load-balancing-gs.sh

Related resources