After you establish a ClassicLink connection, you can connect Elastic Compute Service (ECS) instances in a classic network to the cloud resources deployed in a virtual private cloud (VPC).


Before you can establish a ClassicLink connection, make sure that the following conditions are met:
  • You have read and understand the limits on establishing a ClassicLink connection. For more information, see Overview.
  • The ClassicLink feature is enabled for the VPC to which the ClassicLink connection is established. 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 of the ECS instance.
  4. On the Instances page, find the ECS instance that you want to manage and choose More > Network and Security Group > Set classic link in the Actions column.
  5. In the Connect to VPC dialog box, select a VPC and click OK.
  6. Click Go to the instance security group list and add ClassicLink rules, and click Add ClassicLink Rule.
  7. In the Add ClassicLink Rule dialog box, set the following parameters and click OK.
    Parameter Description
    Classic Security Group Displays the name of the security group of the classic network.
    Select VPC Security Group Select a security group of the VPC.
    Authorization Method Select one of the following authorization methods:
    • Classic <=> VPC: allows the ECS instance in the classic network and cloud resources in the VPC to access each other. This method is recommended.
    • VPC => Classic: allows the cloud resources in the VPC to access the ECS instance in the classic network.
    • Classic => VPC: allows the ECS instance in the classic network to access cloud resources in the VPC.
    Protocol Type Select the protocol for communication.
    Port Range Specify the ports that are used for communication. Specify the ports in the xx/xx format. For example, to specify port 80, enter 80/80.
    Priority Specify a priority for the rule. A smaller value specifies a higher priority.
    Description Enter a description for the security group.
  8. Return to the ECS console and click Parameter on the Instances page. In the Column Filters dialog box, select Connection Status and click OK. Then, you can view the Connection Status of the ECS instance on the Instances page.
    In the Connection Status column, you can view that the ECS instance is in the Connected state. You can also view the ID of the connected VPC.