What type of IP address is known to change when an EC2 instance is stopped and started?

The type of IP address that is known to change when an EC2 instance is stopped and started is the public IP address. When an EC2 instance is launched, it is assigned a public IP address that is dynamic in nature. This means that if the instance is stopped (as in halted or terminated, but not terminated entirely) and then started again later, it will receive a new public IP address. This is a standard behavior for dynamically assigned public IPs in AWS.

In contrast, Elastic IPs are static IPs designed for dynamic cloud computing and remain associated with the AWS account even when the instance is stopped. Private IP addresses are also static for the lifetime of the instance; they do not change when the instance is stopped and started, making them consistent within the same Virtual Private Cloud (VPC). The term static IP is not specifically used in the context of AWS in the same way as Elastic IPs, which are explicitly designed to be persistent and reassignable.

Understanding this behavior is crucial for managing access to resources and ensuring that applications relying on specific public IP addresses are configured correctly, particularly in environments that may frequently stop and start instances.