How to retain an instance's IP address, How to retain an elastic network interface after an instance is released-Elastic Compute Service(ECS)-阿里云帮助中心

By default, when you release an instance, its attached elastic network interfaces (ENIs) are also deleted. You can configure an ENI to be retained when its instance is released. This allows you to attach the ENI to a new instance and reuse its network configuration, such as its IP addresses, routes, MAC address, and security group memberships. Reusing the configuration reduces setup time for instance replacements or failovers.

Limitations

Secondary ENIs can be retained in all regions. Primary ENI retention is currently available only in specific regions.

Supported regions for primary ENI retention

Area	Region name	Region ID
Asia-Pacific - China	China (Ulanqab)	cn-wulanchabu
	China (Shenzhen)	cn-shenzhen
	China (Guangzhou)	cn-guangzhou
	China (Chengdu)	cn-chengdu
	China (Hong Kong)	cn-hongkong
	China (Hohhot)	cn-huhehaote
	China (Zhangjiakou)	cn-zhangjiakou
	China (Hangzhou)	cn-hangzhou
	China (Qingdao)	cn-qingdao
	China (Beijing)	cn-beijing
	China (Shanghai)	cn-shanghai
	China (Heyuan)	cn-heyuan
Asia-Pacific - Other	Singapore	ap-southeast-1
	Malaysia (Kuala Lumpur)	ap-southeast-3
	Indonesia (Jakarta)	ap-southeast-5
	Philippines (Manila)	ap-southeast-6
	Thailand (Bangkok)	ap-southeast-7
	Japan (Tokyo)	ap-northeast-1
	South Korea (Seoul)	ap-northeast-2
Europe & Americas	US (Silicon Valley)	us-west-1
	Germany (Frankfurt)	eu-central-1
	UK (London)	eu-west-1
	US (Virginia)	us-east-1

Configure ENI retention

When you release an instance, your choice to retain or delete an ENI affects the following associated resources:

Resource	Released with instance	Retained after release
Private IPv4 addresses and IPv4 prefixes	Released	Retained
Private IPv6 addresses, IPv6 prefixes, and IPv6 Internet bandwidth	Released	Retained
EIP	Disassociated. You must manually release the EIP or attach it to another resource.	Association retained
security group	Disassociated. The system does not automatically delete the related security group rules.	Association retained
Entries in a Virtual Private Cloud (VPC) route table that point to the ENI	Deleted	Retained

Console

Locate the target ENI in one of the following ways:
- Go to the ECS console and click the ID of the target instance to go to the instance details page. On the instance details page, switch to the ENIs tab and find the target ENI in the ENIs list.
- Go to the ECS Console - Elastic Network Interfaces page and find the target ENI in the ENIs list.
In the Instance column, enable or disable Delete on instance release as needed.

A retained primary ENI becomes a secondary ENI. When you create a new instance, you can assign this ENI as the primary ENI of that instance.

API

When you call the CreateNetworkInterface operation to create an elastic network interface, use the DeleteOnRelease parameter to set its release policy.
Call ModifyNetworkInterfaceAttribute and use the DeleteOnRelease parameter to modify the network interface's release policy.
Call DescribeNetworkInterfaceAttribute to query the release policy of the network interface. The DeleteOnRelease field indicates the release policy.

Attach an ENI to an instance

You can reuse a retained ENI. In the same zone, you can attach it to an existing instance or attach it during instance creation.