What is EIP?

An elastic IP (EIP) is a public IP address that you can purchase and use as an independent resource. You can associate an EIP with an Elastic Compute Service (ECS) instance, an internal-facing Classic Load Balancer (CLB) instance, an internal-facing Application Load Balancer (ALB) instance, a secondary elastic network interface (ENI), a NAT gateway, or a high-availability virtual IP address (HAVIP). If you want to associate an EIP with an ECS instance, CLB instance, or secondary ENI, make sure that the cloud resource with which you want to associate the EIP is deployed in a virtual private cloud (VPC).

An EIP is a NAT IP address provisioned on the Internet-facing gateway and is mapped to the associated cloud resource by using NAT. After an EIP is associated with a cloud resource, the cloud resource can use the EIP to communicate with the Internet.