This topic provides answers to some frequently asked questions about the features, benefits, and limits of elastic IP addresses (EIPs).
- What is an EIP?
- What are the benefits of EIPs?
- What are the differences between an EIP and a static public IP address of an ECS instance?
- How many EIPs can I apply for with an Alibaba Cloud account?
- Is the number of times that I can call EIP operations limited?
- Can I resolve the domain name of a website to an EIP?
- Why am I unable to modify the description of an EIP?
What is an EIP?
An EIP is a public IP address that you can purchase and use as an independent resource. You can associate EIPs with Elastic Compute Service (ECS) instances, internal-facing Server Load Balancer (SLB) instances, secondary elastic network interfaces (ENIs), NAT gateways, and high-availability virtual IP addresses (HAVIPs). The ECS instances, internal-facing SLB instances, and secondary ENIs must be deployed in virtual private clouds (VPCs).
EIPs are NAT IP addresses deployed on the Internet-facing gateway of Alibaba Cloud, and are mapped to the associated cloud resources through NAT. After EIPs are associated with cloud resources, the cloud resources can use the EIPs to communicate with the Internet.
What are the benefits of EIPs?
- Allow you to purchase and use as independent resources
You can purchase and use an EIP as an independent resource. EIPs are not bundled with other computing or storage resources.
- Allow you to associate with resources anytime
You can associate an EIP with a cloud resource as needed. You can also disassociate and release an EIP anytime to prevent unexpected charges.
- Allow you to adjust the maximum bandwidth on demand
You can modify the maximum bandwidth of an EIP based on your business requirements. The modification immediately takes effect.
- Support flexible billing and lower costs
Multiple billing methods are supported, including subscription, pay-by-bandwidth, and pay-by-data-transfer. You can associate an EIP with an EIP bandwidth plan to reduce bandwidth costs.
What are the differences between an EIP and a static public IP address of an ECS instance?
| Item | EIP | Static public IP address |
|---|---|---|
| Supported network | VPC | VPC and classic network |
| Used as an independent resource | Supported | Not supported |
| Associated with and disassociated from an ECS instance anytime | Supported | Not supported |
| Displayed in the ENI information of the associated ECS instance | Cut-through mode: Displayed | Classic network: Displayed VPC: Not displayed |
How many EIPs can I apply for with an Alibaba Cloud account?
You can apply for at most 20 EIPs with an Alibaba Cloud account. To apply for more EIPs, request a quota increase. For more information, see Manage EIP quotas.
Is the number of times that I can call EIP operations limited?
Yes. You can call EIP operations at most 500 times within one day. Subsequent API calls that are sent within the day are throttled.
Can I resolve the domain name of a website to an EIP?
Yes. You can create a DNS record to resolve a domain name to an EIP or a private IP address. For more information, see Add an A record to a website domain.
Why am I unable to modify the description of an EIP?
In most cases, you can modify the description of an EIP on the details page. However, you cannot modify the description if an EIP is hosted by a third party. For example, you cannot modify the description of an EIP that is automatically created by the system when you create an Internet-facing Network Load Balancer (NLB) instance.