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Community Blog What Is Elastic IP Address

What Is Elastic IP Address

This article will show you the definition of Elastic IP Address, and the benefits, limits applied to Elastic IP Address.

Elastic IP Address Overview

An Elastic IP Address (EIP) is a public IP address that you can purchase and hold as an independent resource. You can associate an Elastic IP Address 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 Elastic IP Address 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 Elastic IP Address is associated with a cloud resource, the cloud resource can connect to the Internet by using this Elastic IP Address.

Differences between an Elastic IP Address and a public IP address of an ECS instance

The Elastic IP Address and a public IP address has the following difference:

  • The Elastic IP Address supports VPC network, while the public IP address supports VPC and classic network;
  • The Elastic IP Address supports for being held as an independent resource, while the public IP address not;
  • The Elastic IP Address supports for being associated with and disassociated from an ECS instance at any time, while the public IP address not;

The Benefits of Elastic IP Address

Elastic IP Address has 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.

The Limits of Elastic IP Address

Elastic IP Address (EIP) imposes limits on its features. We recommend that you understand the limits before you use the features.

General limits of Elastic IP Address

  • You can apply for up to 20 Elastic IP Address for each Alibaba Cloud account.
  • An Elastic IP Address can be associated with only one cloud resource and the EIP to be associated must be in the Available state. An EIP takes effect immediately after it is associated with a cloud resource.
  • Elastic IP Address that is locked for security reasons cannot be released, associated with cloud resources, or disassociated from cloud resources.

Limits on associating an Elastic IP Address with an ECS instance

Take note of the following limits before you associate an EIP with an Elastic Compute Service (ECS) instance:

  • The ECS instance must be deployed in a virtual private cloud (VPC).
  • The ECS instance and the EIP must be deployed in the same region.
  • The ECS instance must be in the Running or Stopped state.
  • The ECS instance is not associated with a static public IP address or another Elastic IP Address.
  • Each ECS instance can be associated with only one EIP. If you want to associate multiple EIPs with an ECS instance, you can associate the EIPs with a secondary elastic network interface (ENI) and associate the secondary ENI with the ECS instance.

Limits on associating an Elastic IP Address with a NAT gateway

Take note of the following limits before you associate an Elastic IP Address with a NAT gateway:

  • Before January 26, 2018, no NAT bandwidth plan was purchased under the Alibaba Cloud account to which the NAT gateway belongs.
  • The NAT gateway and the EIP must be deployed in the same region.
  • You can associate a NAT gateway with at most 20 EIPs, among which up to 10 pay-by-data-transfer EIPs can be associated.

Limits on associating an Elastic IP Address with an SLB instance

Take note of the following limits before you associate an Elastic IP Address with a Server Load Balancer (SLB) instance:

  • The SLB instance must be deployed in a VPC.
  • The SLB instance and the Elastic IP Address must be deployed in the same region.
  • Each SLB instance can be associated with only one Elastic IP Address.

Limits on associating an Elastic IP Address with a secondary ENI

Take note of the following limits before you associate an Elastic IP Address with a secondary ENI:

  • The secondary ENI must be deployed in a VPC.
  • The secondary ENI and the Elastic IP Address must be deployed in the same region.
  • You can associate an Elastic IP Address with a secondary ENI in one of the following modes: NAT mode, cut-through mode, and multi-EIP to ENI mode.

Conclusion

Independent public IP address resources can be bound to Alibaba Cloud VPC-type ECS instances, NAT gateway, and Intranet Server Load Balancer. Also, they can be dynamically unbound, which decouples public IP addresses from ECS instances, NAT gateway, and Server Load Balancer, meeting the needs for flexible management.

Related Product

Elastic IP Address

An independent public IP resource that decouples ECS and public IP resources, allowing you to flexibly manage public IP resources.

Related Blog

Configuring and Mapping Multiple EIPs to ENI Using NAT Gateway

Initially, each Alibaba Cloud Elastic Network Interface (ENI) could have only a single Private IP Assigned to it. One could assign multiple Network Cards to an instance depending on the Instance type. However, we have new functionality that will allow assigning of Multiple Private IP's to one ENI. Besides, we can use the NAT Gateway to Map an Elastic IP to every Private IP that is assigned to an ENI. This allows having multiple EIP's assigned to an Elastic Compute Service (ECS) Instance in NAT Mode.

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