legacy application that has hard-coded static IP addresses and is running on an EC2 instance, what is the best failover solution that allows you to keep the same IP address on a new instance

If you have a legacy application running on an EC2 instance with hard-coded static IP addresses and you want to implement a failover solution while maintaining the same IP address on a new instance, one approach is to use an Elastic IP (EIP) address in combination with an Auto Scaling Group. Here's a general outline of the steps you can take:

1. Allocate an Elastic IP (EIP):

• Allocate an Elastic IP address in the AWS Management Console. EIPs are public IP addresses that you can attach to your EC2 instances.

2. Associate the EIP with the Current EC2 Instance:

• Associate the allocated EIP with your existing EC2 instance. This gives your EC2 instance a fixed public IP address (EIP).

3. Create an Amazon Machine Image (AMI) of the EC2 Instance:

• Create an AMI of your existing EC2 instance. This AMI will be used to launch a new instance in the event of a failure.

4. Configure an Auto Scaling Group (ASG):

• Create an Auto Scaling Group that uses the AMI created in the previous step. Ensure that the ASG is configured to launch instances in the same subnet as the original EC2 instance.

5. Configure Health Checks:

• Set up health checks in the Auto Scaling Group to monitor the health of your application. If the health checks fail, the Auto Scaling Group can replace the unhealthy instance.

6. Attach the EIP to the New Instance:

• Create a script or use AWS CLI commands to automatically associate the Elastic IP with the new instance when it is launched by the Auto Scaling Group.

7. Adjust Security Group Rules:

• Ensure that the security group rules are configured to allow traffic to and from the necessary ports for your application.

With this setup, if the original EC2 instance becomes unhealthy or fails, the Auto Scaling Group will launch a new instance using the specified AMI. The script or automation will associate the EIP with the new instance, allowing it to take over the original IP address. This helps in maintaining the same IP address during failover.

Keep in mind that this is a high-level overview, and you should adapt the configuration based on your specific requirements and the characteristics of your legacy application. Additionally, consider the potential downtime during the failover process and implement strategies to minimize any service disruptions.