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Server Load Balancer:Manage default server group

Last Updated:Mar 07, 2025

Each Classic Load Balancer (CLB) instance has one and only one default server group. You need to add backend servers to the default server group to use it. This server group can be specified to process traffic forwarded by all listeners of a CLB instance.

Prerequisites

The backend servers to be added to the default server group of a CLB instance must be in the same region as the CLB instance.

Add backend servers to the default server group

  1. Log on to the CLB console.
  2. In the top navigation bar, select the region where the CLB instance is deployed.

  3. On the Instances page, click the ID of the CLB instance.

  4. Click the Default Server Group tab and click Add.

  5. In the Servers panel, select a backend server type and a backend server, and click Next.

    • To add an Elastic Compute Service (ECS) instance, select ECS/ENI and select the ECS instance in the instance list.

    • To add an elastic network interface (ENI) attached to an ECS instance, select ECS/ENI and enable Advanced Mode. Click the plus icon next to the ECS instance and select the ENI. If no ENIs are attached to an ECS instance, there is no plus icon next to it. For information about attaching an ENI to an ECS instance, see Bind a secondary ENI.

    • To add an Elastic Container Instance, select ECI and select the Elastic Container Instance in the instance list.

  1. In the Ports/Weights step, specify a weight for the backend server you selected and click Add.

    Weight settings work when you use the Weighted Round Robin (WRR) scheduling algorithm for a listener of the CLB instance. A backend server that has a higher weight will receive more requests.

    Important
    • The valid values of Weight range from 0 to 100. A backend server with a weight of 0 will not receive any requests.

    • In this step, port settings are not involved. After adding backend servers to the default server group, you can specify server ports to use when you create a listener. Note that for the same listener, the server ports used in the default server group must be the same.

  2. In the Servers to Add panel, confirm the configurations and click OK. In the message that appears, click OK.

    To add more backend servers, click Add More.

Manage backend servers in the default server group

After adding backend servers to the default server group, you can modify the weights of the backend servers. If you do not want a backend server to forward network traffic, remove the backend server.

  1. Log on to the CLB console.
  2. In the top navigation bar, select the region where the CLB instance is deployed.

  3. On the Instances page, click the ID of the CLB instance.

  4. Click the Default Server Group tab and manage the backend servers.

    • Modify the weights:

      1. Find the backend server that you want to manage, move the pointer over the weight specified for it, and click the 铅笔 icon.

      2. In the dialog box that appears, modify the weight and click OK.

        Important

        Valid values: 0 to 100. If the weight of a backend server is set to 0, no requests are sent to the backend server.

    • Remove a backend server:

      1. Find the backend server that you want to remove and click Remove in the Actions column.

      2. In the message that appears, click Remove.

References

To use API operations to manage the default server group, refer to the following topics: