This topic describes how to establish a ClassicLink connection. After you establish a ClassicLink connection, you can connect classic-network ECS instances to the cloud resources deployed in a VPC.


Before you can establish a ClassicLink connection, the following conditions must be met:
  • The limits for establishing ClassicLink connections are known. For more information, see ClassicLink overview.
  • The ClassicLink feature in the VPC in which you want to establish a ClassicLink connection is enabled. For more information, see Enable ClassicLink.


  1. Log on to the ECS console.
  2. In the left-side navigation pane, choose Instances & Images > Instances.
  3. Select the region to which the target ECS instance belongs.
  4. On the Instances page, find the target classic-network instance, and then choose More > Network and Security Group > Set classic link in the Actions column.
  5. In the Connect to VPC dialog box, select the target VPC, and then click OK.
  6. Click Go to the instance security group list and add ClassicLink rules, and then click Add ClassicLink Rule.

    Add a ClassicLink rule
  7. In the Add ClassicLink Rule dialog box, set the parameters, and then click OK. The following table describes the parameters.
    Configuration Description
    Classic Security Group The name of the classic network security group.
    Select VPC Security Group Select the security group of the VPC.
    Mode Select one of the following modes:
    • Classic <=> VPC: The connected resources can access each other (recommended).
    • Classic => VPC: Authorize the classic-network ECS instance to access cloud resources in the VPC.
    • Classic <= VPC: Authorize the cloud resources in the VPC to access the classic-network ECS instance.
    Protocol Type Select the protocol for communication.
    Port range Select the port for communication. The port must be in the format of xx/xx. For example, if port 80 is used, enter 80/80.
    Priority Set the priority for the security group rule. A smaller value indicates a higher priority.
    Description Enter a description for the security group rule.
  8. On the ECS instances page, click the Column Filter icon in the upper-right corner, select Connection Status, and then click OK to view the connection status of the ECS instance.
    Figure 1. Column Filters icon

    Column Filters icon
    Figure 2. Connection Status

     Connection Status
    Figure 3. Connected to a VPC

    Connected to a VPC