This topic provides an overview of Elastic IP Address. An elastic IP address (EIP) is a public IP address that you can purchase and hold as an independent resource. You can associate an EIP with an Elastic Compute Service (ECS) instance deployed in a virtual private cloud (VPC), an internal Server Load Balancer (SLB) instance deployed in a VPC, or a secondary elastic network interface (ENI) attached to a VPC. You can also associate an EIP with a NAT gateway, or a High-Availability Virtual IP Address (HAVIP).

An EIP is also a NAT IP address that is provisioned in a public-facing gateway of Alibaba Cloud and is mapped to the associated cloud resource with NAT. After an EIP is associated with a cloud resource, the cloud resource can connect to the Internet by using this EIP.

Differences between an EIP and a public IP address of an ECS instance

The following table compares the features of an EIP with those of a public IP address of an ECS instance.

Feature EIP ECS public IP address
Supported networks VPC VPC and classic network
Support for being held as an independent resource Yes No
Support for being associated with and disassociated from an ECS instance at any time Yes No
Support for being displayed in the ENI information of the associated ECS instance The IP address is displayed in the ENI information if it is associated with the ENI in the cut-through mode or multi-EIP to ENI mode

Classic network: Yes

VPC: No

Benefits

EIPs have the following benefits:
  • Independent purchase and possession

    You can purchase and hold an EIP as an independent resource. EIPs are not bundled with other computing or storage resources.

  • Flexible association

    You can dissociate an EIP from a cloud resource and then release the EIP if the EIP is no longer needed. This prevents unexpected charges on your account.

  • Configurable network capabilities

    You can adjust the peak bandwidth of an EIP at any time. The bandwidth changes take effect immediately.