An elastic IP address (EIP) is a public IP address that you can purchase and use as an independent resource. EIPs can be retained independently and associated with or disassociated from Elastic Compute Service (ECS) instances in virtual private clouds (VPCs).

Overview

EIPs are NAT IP addresses that are located in the public gateway of Alibaba Cloud. By means of NAT, EIPs are mapped to the primary elastic network interfaces (ENIs) of the ECS instances that are associated with the EIPs. You can associate EIPs with ECS instances that are located in VPCs to enable the instances to communicate over the Internet. Similarly to system-assigned public IP addresses (PublicIP addresses), EIPs remain invisible inside the operating systems of ECS instances.

Advantages

ECS instances located in VPCs support both PublicIP addresses and EIPs. For information about the use scenarios of and differences between these public IP addresses, see IP addresses of ECS instances within VPCs.

The following table describes the advantages of EIPs over PublicIP addresses.

Item PublicIP address EIP
Can the public IP address be independently purchased and used? No Yes
Can the public IP address be associated with or disassociated from an ECS instance as needed? No Yes
Is the public IP address retained when the associated ECS instance is released? No Yes
Maximum number of public IP addresses per ECS instance 1 In multi-EIP-to-ENI mode, multiple EIPs can be associated with a single ECS instance. For more information, see Associate EIPs with secondary ENIs in multi-EIP-to-ENI mode (new applications are not accepted).

Billing methods

EIPs support the subscription and pay-as-you-go billing methods. For more information, see Billing overview.

Limits

EIPs can be associated with ECS instances or ENIs. An EIP can be associated only with an ECS instance that meets the following requirements:

  • The ECS instance is located in a VPC.
  • The ECS instance is located in the same region as the EIP.
  • The ECS instance is in the Running or Stopped state.
  • No public IP addresses are associated with the primary ENI of the ECS instance.

Operations

For more information, see EIP overview.