Currently, for ECS instances of the classic network type, IP addresses are distributed in a unified way and divided into public and private IP addresses. Private IP address are mainly used for remote access to your instance or to the services deployed on your instance.

Intranet IP addresses

Each classic network-connected ECS instance is assigned a private, that is intranet, IP address.

Scenarios

Intranet IP addresses can be used in the following scenarios:

  • Load balancing
  • Mutual intranet access between ECS instances
  • Mutual intranet access between ECS instances and other cloud services, such as OSS and RDS

Traffic generated through intranet IP addresses within an intranet is free of charge. For more information, see Intranet.

Modify an intranet IP address

Once a classic network-connected ECS instance is created, you cannot change its intranet IP address.

Note Do not change an intranet IP address within a guest operating system. Otherwise, communication within an intranet is interrupted.

Public IP addresses

If you purchase bandwidth for Internet access, a public IP address is assigned to your classic network-connected ECS instance. You cannot change the public IP address once it is assigned.

Scenarios

A public IP address is used in the following scenarios:

  • Mutual access between an ECS instance and the Internet
  • Mutual Internet access between ECS instances and other Alibaba Cloud services
Assign a public IP address

When you create an ECS instance, a public IP address is assigned to it if Assign public IP is selected.

For a Subscription instance with no public IP address, you can use the Upgrade Configuration or the Renew for Configuration Downgrade feature to purchase public network bandwidth.

Note
  • For a Pay-As-You-Go classic network-connected ECS instance with no public IP address, you cannot assign a public IP address after the instance is created.
  • For a classic network-connected ECS instance, you cannot disassociate or release its public IP address once the IP address is assigned. If you set the bandwidth to 0 Mbit/s when renewing an instance for configuration downgrade, in the next purchase cycle, the public IP address is retained, but the instance cannot access the Internet.
Billing

You are billed for usage of Internet outbound traffic only. For more information, see Billing of network bandwidth.

Multicast and broadcast

Intranet IP addresses cannot be used for multicasting or broadcasting.