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    Server Load Balancer:Create and manage a CLB instance

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    Server Load Balancer:Create and manage a CLB instance

    Last Updated:Feb 02, 2026

    Classic Load Balancer (CLB) provides basic Layer 4 and Layer 7 load balancing capabilities. It distributes client requests to backend servers to eliminate single points of failure and improve service redundancy and stability.

    Private network access

    An internal-facing CLB instance provides a private IP address within the virtual private cloud (VPC) where the instance resides. Clients that can communicate with this VPC can access the service using the private IP address of the internal-facing CLB instance.

    Console

    Go to the CLB buy page, complete the following configurations, and click Buy Now.

    • SLB region ID: Must match the region where your backend servers are deployed.

    • Zone type:

      • If the selected region supports multiple zones, Multi-zone is selected by default and cannot be changed. The instance is deployed across both a primary and a secondary zone. If the primary zone fails, traffic automatically switches to the secondary zone.

      • If the region has only one zone, only Single zone is supported.

    • Primary zone: Select the zone that currently handles traffic. This setting cannot be changed after creation. To change it, you must create a new instance.

    • Instance type: Select Internal. The private IP address is allocated from the vSwitch CIDR block of the specified VPC.

    • Instance billing method: Pay-by-usage.

      Alibaba Cloud will discontinue sales of pay-by-specification CLB instances starting at 00:00:00 on June 1, 2025 (UTC+8).

    • IP version: Only IPv4 is supported.

    • VPC and vSwitch: Select the VPC and vSwitch in the region and primary zone where you plan to deploy the CLB instance.

    • No Internet data transfer fee is charged for internal-facing instances. After creation, you can bind an EIP to the instance to enable public network access. The EIP enables public access and incurs public network charges.

    • Instance name, tags, and resource group: Set these appropriately to simplify management. After purchase, you can modify the instance name and configure tags to manage the instance on the instance details page.

    API

    Call CreateLoadBalancer and set AddressType to intranet to create an internal-facing CLB instance.

    Public network access

    • Internet-facing CLB instance: The system automatically assigns one fixed public IP address to enable public access. This public IP address is tightly bound to the instance.

      release an Internet-facing IPv4 CLB instance, you can choose to convert the fixed public IP address to an EIP and retain it.
      The fixed public IP address cannot be added to Internet Shared Bandwidth.

    • Bind an EIP to an internal-facing CLB instance (recommended): An EIP enables public access. You can flexibly bind or unbind an EIP from an internal-facing CLB instance. EIPs can be added to Internet Shared Bandwidth to reduce public bandwidth costs.

    Create an Internet-facing CLB instance

    Console

    Go to the CLB buy page, complete the following configurations, and click Buy Now.

    API

    Call CreateLoadBalancer and set AddressType to internet to create an Internet-facing CLB instance.

    Bind an EIP to an internal-facing CLB instance

    • An internal-facing CLB instance supports binding to only one EIP in the same region.

    • After binding an EIP, the associated EIP incurs charges.

    Console

    1. Go to the CLB buy page and purchase an internal-facing CLB instance as described in Create an internal-facing CLB instance.

    2. In the Actions column of the target internal-facing CLB instance, choose 更多 > Modify Instance > Bind EIP.

      Choose an available EIP from the drop-down list. If no EIPs are available, click Purchase EIP and follow the on-screen instructions to purchase a new one.

    API

    1. Call CreateLoadBalancer and set AddressType to intranet to create an internal-facing CLB instance.

    2. Call AssociateEipAddress to bind an EIP.

    Protection settings

    Enable deletion protection and configuration read-only mode to prevent accidental deletion or modification of the instance.

    Configuration read-only mode applies only to the console. API calls can still modify instance configurations.

    Console

    Go to the CLB console - Instances page, click the ID of the target instance to go to the Instance Details page, and then toggle Basic Information to enable or disable Deletion Protection and Configuration Read-only Mode.

    API

    Manage idle instances

    Release idle instances promptly to better manage costs.

    • Criteria: A pay-as-you-go CLB instance is considered idle if it has been unused for more than 7 days and meets any of the following conditions:

      • The instance is in the Stopped state.

      • No listener is configured for the instance.

      • All listeners of the instance are stopped.

      • No backend servers are added to the instance.

      • The weights of all backend servers of the instance are 0.

    • Idle instances continue to incur charges. CLB instances stop incurring charges only after they are released.

    Console

    1. Go to the CLB console - Idle Instances page to view all pay-as-you-go instances that have been unused for more than seven days.

    2. In the upper-right corner of the idle instances list, click 设置 to customize the displayed columns, such as endpoint, region, and reason for idleness.

    3. After confirming that you no longer need the instance, click Release in the Actions column. Before releasing, ensure the CLB instance is not in use to avoid accidental release.

    Clean up resources

    • Prerequisites for release:

      • If deletion protection is enabled, you cannot release the instance. Disable Deletion Protection on the Instance Details page first.

      • Only pay-as-you-go instances can be released.

    • Release behavior:

      • Set Release Now or Scheduled Release as needed. For scheduled release, billing stops at the specified time, and the instance is released at the next full hour.

      • Internet-facing IPv4 CLB instance: When releasing, you can choose whether to disassociate the public IP address, convert it to an EIP, and retain it.

        • The retained EIP can be bound to another instance in the same region, allowing you to keep the same public IP address during instance migration.

          The first time you retain an EIP, the system automatically creates the service-linked role AliyunServiceRoleForSlbEipAccess to allow CLB to access the EIP service.

        • The retained EIP is billed separately. By default, it uses the pay-as-you-go (pay-by-traffic) billing method with a maximum bandwidth of 200 Mbps.

    • Impact of release:

      • After a CLB instance is released, its configurations and data are deleted and cannot be restored.

      • Releasing a CLB instance does not affect your running Elastic Compute Service (ECS) instances.

      Warning

      • If you have resolved a custom domain name to the IP address of a CLB instance, resolve the domain name to another load balancer instance before releasing the CLB instance to avoid service interruption.

      • After a CLB instance is released, its configurations and data are deleted and cannot be restored.

      • If your CLB instance is managed by another Alibaba Cloud service, such as Container Service for Kubernetes (ACK), releasing the CLB instance causes the associated service to become unavailable and unrecoverable.

    Console

    1. Go to the CLB console - Instances page, and in the Actions column of the target instance, choose 更多操作 > Release Settings.

    2. Select Release Behavior. When planning to release now an Internet-facing IPv4 CLB instance, you can choose whether to disassociate the public IP address, convert it to an EIP, and retain it.

    API

    Call DeleteLoadBalancer to release a pay-as-you-go CLB instance.

    Billing

    New CLB instances support only pay-by-usage billing.

    Effective 00:00:00 on June 1, 2025 (UTC+8), Alibaba Cloud will discontinue the sale of pay-by-specification CLB instances.

    • Internet-facing CLB instance: Incurs instance fees, public IP retention fees, LCU fees, and public network fees.

    • Internal-facing CLB instance: Incurs instance fees and LCU fees. After binding an EIP, the EIP incurs separate charges.

    Quotas

    Resource

    Default limit

    Increase quota

    Number of CLB instances that can be created under one Alibaba Cloud account (main account)

    30 items

    Increase your quota using either of the following methods:

    References

    • CLB server groups: Server groups route business requests distributed by CLB to the appropriate backend servers.

    • CLB listeners: Listeners check connection requests and distribute traffic to backend servers based on scheduling algorithms.

    • Configure domain name resolution: CLB provides services through IP addresses. Resolve your custom domain name to the CLB instance's endpoint to access the service via the domain name.