CLB routes requests to real server instances that are running normally. This document describes how to add or delete real servers as needed or when you use CLB for the first time.

• Unbinding a real server will unbind the CLB instance from the CVM instance, and CLB will stop forwarding requests to it immediately.
• Unbinding a real server will not affect the lifecycle of your CVM instance, which can be added to the real server cluster again when necessary.
• If a CLB instance is associated with an auto scaling group, CVMs in the group will be automatically added to the real servers of CLB. When a CVM instance is removed from the auto scaling group, it will be automatically deleted from the real servers of CLB.

CLB

Adding real server to CLB instance

1. Log in to the CLB Console and click the corresponding CLB instance ID to enter the CLB details page.
2. In the listener corresponding to the CLB instance, add a real server.
   • TCP/UDP listener
     When adding a real server, select the listener to be bound in the left column and click Bind. Read the following instructions for operating details.
     
   • HTTP/HTTPS Listener
     When adding a backend CVM instance, select the listener and rule to be bound to in the left column and click Bind.
     
3. In the pop-up window, select the CVM instance that needs to be associated with, enter the port and weight, and click OK to associate the CVM instance with the CLB instance.

   The pop-up window only displays available CVM instances in the same region and same network environment that are not isolated and have not expired with peak bandwidth greater than 0.

   
4. To bind CVMs that have the same preset port value in batches, enter the preset port value in the "Default Port" field, select the corresponding CVMs, configure the weights, and click OK to bind them in batches.
   

   If you need to use API to add real servers, please see RegisterInstancesWithLoadBalancer API.

Modifying real server weight for CLB instance

The real server weight determines the number of CVM requests to be forwarded. When binding a real server, you need to preset its weight. To modify the weight, refer to the steps below. For more information on CLB real server weight, please see CLB Polling Method.

1. Log in to the CLB Console and click the corresponding CLB instance ID to enter the CLB details page.
2. Select the instance and listener rule, select the corresponding CVM from the list, click Edit, enter the new weight, and click Submit to modify the weight of the CVM.
3. To modify the weights in batches, select all relevant CVM instances, click Modify Weight, enter the new weight, and then click Submit.
   

If you need to use an API to modify real server weights, please see ModifyLoadBalancerBackends API.

Modifying real server port for CLB instance

1. Log in to the CLB Console and click the corresponding CLB instance ID to enter the CLB details page.
2. Select the instance and listener rule, select the corresponding CVM from the list, click Edit, enter the new port, and click Submit to modify the port of the CVM.
3. To modify the ports in batches, select all relevant CVM instances, click Modify Port, enter the new port, and then click Submit.
   

If you need to use API to modify real server ports, please see ModifyTargetPort.

Unbinding real server from CLB instance

1. Log in to the CLB Console and click the corresponding CLB instance ID to enter the CLB details page.
2. Select the listener and rule, select from the list on the right the CVM to be unbound, click Unbind, and then click Submit in the pop-up window.
3. To unbind CVM instances in batches, select all CVM instances that need to be unbound, click Unbind, and then click Submit in the pop-up window.
   

If you need to use API to unbind real servers, please see DeregisterTargets API.

Classic CLB

Adding real server to CLB instance

1. Log in to the CLB Console and click the corresponding CLB instance ID to enter the CLB details page.
2. When binding a real server, you need to specify the real server port during listener creation. Click Create, enter the port value in the "Backend Port" field, and then click Next to complete subsequent configuration.
   
3. Click Bind, select the CVM instance to be bound, enter the weight, and click OK to bind it.

   The pop-up window only displays available CVM instances in the same region and same network environment that are not isolated and have not expired with peak bandwidth greater than 0.

   

If you need to use an API to add a real server, please see RegisterTargetsWithClassicalLB API.

Modifying real server weight for CLB instance

1. Log in to the CLB Console and click the corresponding CLB instance ID to enter the CLB details page.
2. Select the corresponding CVM from the list below the listener, click Modify Weight, enter the new weight, and click Submit to modify the weight of the CVM.
3. To modify the weights in batches, select all relevant CVM instances, click Modify Weight, enter the new weight, and then click Submit.
   

Currently, real server weight cannot be modified through APIs.

Unbinding real server from CLB instance

1. Log in to the CLB Console and click the corresponding CLB instance ID to enter the CLB details page.
2. Select the corresponding CVMs from the list below the listener, click Unbind, and click Submit in the pop-up window.
3. To unbind CVM instances in batches, select all CVM instances that need to be unbound, click Unbind, and then click Submit in the pop-up window.
   

If you need to use API to unbind real servers, please see DeregisterTargetsFromClassicalLB API.