IP addresses are used to connect to ECS instances or their deployed services. ECS instances within the classic network can be assigned two types of IP addresses: internal IP addresses and public IP addresses.

Internal IP addresses

Each new ECS instance within the classic network is assigned an internal IP address for communication over the internal network. For more information about internal network communication, see Intranet.

Internal IP addresses can be used in the following scenarios:
  • Load balancing
  • Communication over the internal network between ECS instances within the same LAN
  • Communication over the internal network between an ECS instance and other cloud services such as OSS and ApsaraDB RDS within the same LAN

Public IP addresses

If you select a public network bandwidth greater than 0 Mbit/s when you purchase an ECS instance within the classic network, the system assigns a public IP address to the instance.

Public IP addresses can be used in the following scenarios:
  • Communication between ECS instances and the Internet
  • Communication between an ECS instance and other cloud services that are not within the same LAN
Note After the system assigns a public IP address, you cannot release or disassociate the public IP address. If you set the public bandwidth of an instance to 0 Mbit/s by downgrading configurations during renewal or changing the bandwidth of a pay-as-you-go instance, the instance cannot be connected to the Internet but the public IP address is retained.

Billing

Communication traffic generated by using internal IP addresses is free of charge.

You are billed only for outbound Internet traffic. For more information, see Public bandwidth.

Configurations

  • Internal IP addresses

    The internal IP addresses of ECS instances within the classic network are assigned by the system and cannot be modified. Do not change an internal IP address within the operating system. Otherwise, communication within the internal network may be interrupted.

  • Public IP addresses

Multicasting and broadcasting

Internal IP addresses of ECS instances within the classic network do not support multicasting or broadcasting.