When you manually release an Elastic Compute Service (ECS) instance that is located in the classic network, you can convert the system-assigned public IP address of the instance into an elastic IP address (EIP). EIPs can be associated with ECS instances that are located in virtual private clouds (VPCs) for variety of scenarios such as network migration and flexible bandwidth adjustment. You can convert the system-assigned public IP address of an ECS instance that is located in the classic network into an EIP only when you manually release the instance.
Prerequisites
- The instance is assigned a public IP address.
- If the instance is a pay-as-you-go instance, it is in the Stopped state and you do not have overdue payments in your account.
- If the instance is a subscription instance, it is in the Expired state.
Note If a subscription instance in the classic network is in the Expired state, you can directly release the instance. When you release the instance, you can convert its system-assigned public IP address into an EIP. If a subscription instance in the classic network has not expired, you can change the instance billing method to pay-as-you-go and then release the instance. When you release the instance, you can convert its system-assigned public IP address into an EIP. For more information, see Change the billing method of an instance from subscription to pay-as-you-go.
- If the instance is a subscription instance, the instance uses the pay-by-traffic billing method for network usage. You can change the billing method for network usage from pay-by-bandwidth to pay-by-traffic by upgrading or downgrading instance configurations. For more information, see Overview of instance configuration changes.
- If the configurations of the instance were changed, the new configurations already take effect.
- Snapshots are created to back up data and prevent data loss caused by accidental operations. For more information, see Create a snapshot.
Background information
After you convert the system-assigned public IP address of an ECS instance in a classic network into an EIP, take note of the following items:
- The EIP is billed on a pay-by-data-transfer basis.
- The public bandwidth of the EIP is the same as that of the ECS instance. You can increase the public bandwidth of the EIP in the VPC console. However, if the public bandwidth of the ECS instance is 0 Mbit/s, the public bandwidth of the EIP is 1 Mbit/s.
- The EIP cannot be associated with an ECS instance located in the classic network.
- Unlike ECS instances in VPCs, ECS instances in the classic network have public network interface controllers (NICs). After the system-assigned public IP address of an ECS instance in the classic network is converted into an EIP, the public NIC is unbound from the instance and the MAC address of the NIC is released.
Procedure
Result

What to do next
You can associate the EIP with another ECS instance. For more information, see Associate an EIP with an instance.