An Elastic IP Address (EIP) is an independent public IP address that you can purchase and use. EIPs can be associated to different ECS instances that reside within VPCs over time to allow access to the ECS instances.
EIPs are NAT IP addresses that are located in the public gateway of Alibaba Cloud. Through NAT, EIPs are mapped to the NICs in internal networks of the ECS instances that are associated with the EIPs. You can associate EIPs to ECS instances that reside within VPCs to enable the instances to communicate with the public network. However, you cannot view the EIPs on the NICs of the ECS instances.
Public IP addresses are automatically assigned to ECS instances when you configure public bandwidth for the instances. Compared with these public IP addresses, EIPs provide more flexibility for purchase and management. The following table compares public IP addresses assigned to ECS instances and EIPs.
|Item||Public IP address assigned to an ECS instance||EIP|
|Can the IP address be independently purchased and used?||No||Yes|
|Can the IP address be associated to or disassociated from an ECS instance as needed?||No||Yes|
|Can the bandwidth value for the IP address be adjusted in real time?||Yes||Yes|
EIPs can be billed by traffic or by bandwidth. For more information, see EIP document Billing method.
An EIP can be associated only to an ECS instance that meets the following requirements:
- The ECS instance resides within a VPC.
- The ECS instance is in the same region as the EIP.
- The ECS instance is in the Running or Stopped state.
- The ECS instance is not associated with system-assigned public IP addresses or EIPs.
Create an EIP
You can create an EIP and associate it to an ECS instance that resides within a VPC and is not assigned public IP addresses. For more information, see Create an EIP.
You can follow these steps to allow an ECS instance that resides within a VPC to have one system-assigned public IP address and multiple EIPs: Associate multiple EIPs to an ENI by selecting the Multi-EIP to ENI mode and attach the ENI to the ECS instance. Set the Multi-EIP to ENI mode
Release an EIP
If you no longer need an EIP, disassociate it from the ECS instance and then log on to the EIP console to release it. For more information, see Disassociate an EIP from a cloud instance.