If you have traditional active/standby requirements, where one backend server is used as the master server and the other is used as the slave server, create a master-slave server group. When the master server works normally, requests are distributed to it; when the master server is down, the requests will be distributed to the slave server to avoid service interruption.


  • You have created an SLB instance.
  • You have created ECS instances and deploy applications to process distributed requests. 

Background information

After a master-slave server group is configured for a listener, the listener will forward requests to the ECS instances in the server group instead of the ECS instances in the backend server pool.
Only Layer-4 listeners (TCP and UDP protocols) support configuring master-slave server groups.


  1. Log on to the SLB console.
  2. On the Instances page, select a region.
  3. Click the ID of an SLB instance.
  4. In the left-side navigation pane, click Server > Master-Slave Server Groups.
  5. On the Master-Slave Server Group page, click Master-Slave Server Group.
  6. In the Master-Slave Server Group dialog box, complete these steps:
    1. Enter a group name in the Group Name field.
    2. Select the network type for the ECS instance you want to add.
    3. In the Available Servers, select the ECS instances to add.
    4. In the Selected Servers list, enter the port number and weight for each added ECS instance, and then select one ECS instance as the slave server. Click Confirm.