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Create and manage CLB instances

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Classic Load Balancer (CLB) distributes client requests across backend servers at Layer 4 and Layer 7, eliminating single points of failure and improving application availability and stability.

Internal access

An internal CLB instance receives a private IP address within its VPC. Clients with connectivity to the VPC can access your service through this IP address.

Console

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

  • Region and Zone: Fixed after creation. For an internal CLB instance, the private IP address, availability zone, and vSwitch binding also cannot be changed after creation. To change any of these configurations (for example, to migrate an instance due to a zone decommission), you must create a new CLB instance, migrate your workloads to the new instance, and then release the old instance.

    • Region: Select the region where your backend servers are deployed. Backend ECS instances only need to be in the same region as the CLB instance. The availability zone does not need to match.

    • Zone: After you select a region, the system automatically assigns a primary zone to serve traffic. The primary and secondary zones cannot be changed after the instance is created.

  • Zone Type:

    • If a region supports multiple availability zones, Multi-zone is selected by default and cannot be changed. The instance deploys across primary and secondary zones for automatic failover. A CLB instance with Multi-zone deployment can mount ECS instances from any zone within the same VPC as backend servers.

    • In regions with only one availability zone, only Single-zone is supported.

  • InstanceChargeType: PayByCLCU.

    Effective 00:00:00 (UTC+8) on January 1, 2026, Alibaba Cloud will stop selling CLB instances that are billed by specification.

  • Instance Type: Select Internal Network to allocate a private IP from the specified vSwitch CIDR block. The console does not support manually specifying a private IP address. To use a specific private IP address, see Specify a private IP address when creating a CLB instance by using OpenAPI.

  • VPC: Select the VPC and vSwitch in the region and primary zone for the CLB instance. When adding backend servers, the selected servers must belong to the same VPC. The availability zone of the backend servers does not need to match the CLB instance's zone.

  • IP Version: Only IPv4 is supported.

  • Internet Data Transfer Fee: Internal instances do not incur data transfer fees. After creation, you can bind an EIP to the instance to enable Internet access. The EIP provides Internet access and incurs data transfer fees.

  • Instance Name, Tag, and Resource Group: Specify these to simplify management. After purchase, you can modify the instance name and configure tags on the details page.

API

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

Internet access

  • Internet-facing CLB instance: The system assigns a static public IP address bound to the instance for Internet access.

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

  • Bind an EIP to an internal CLB instance (Recommended): An EIP provides Internet access and can be flexibly bound or unbound. You can add EIPs to an Internet Shared Bandwidth instance to reduce data transfer costs.

Create an Internet-facing CLB instance

Console

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

API

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

Bind an EIP to an internal CLB

  • You can bind an EIP or an Anycast EIP to an internal CLB instance.

  • An intranet CLB instance can be bound to only one EIP or Anycast EIP. If your workload requires multiple public entry points, use ALB or NLB, which support binding multiple EIPs.

    • To bind an EIP, the intranet CLB instance and the EIP must be in the same region.

    • Only CLB instances in the following regions support binding an Anycast EIP.

      Area

      Region

      Asia Pacific - China

      China (Hong Kong)

      Asia Pacific - Other

      Philippines (Manila), Japan (Tokyo), Singapore, Malaysia (Kuala Lumpur), Indonesia (Jakarta), South Korea (Seoul), Thailand (Bangkok)

      Europe and the Americas

      US (Silicon Valley), US (Virginia), Germany (Frankfurt), UK (London)

  • After you bind an EIP or Anycast EIP, the IP address incurs fees.

  • Both pay-as-you-go and subscription EIPs can be bound. Before binding, ensure that the EIP is in the same region as the CLB instance and is in the Available state.

Console

  1. Go to the CLB buy page and create an intranet CLB instance. Create an intranet CLB instance.

  2. In the Actions column of the target internal CLB instance, choose More > Change Specification > Bind EIP.

    • IP Type: Select EIP or Anycast EIP.

    • IP Address: Select an available EIP or Anycast EIP. If no IP addresses are available, click Purchase EIP or Purchase Anycast EIP and follow the on-screen instructions to purchase one.

API

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

  2. Call AssociateEipAddress to bind an EIP, or call AssociateAnycastEipAddress and set BindInstanceType to SlbInstance to bind an Anycast EIP.

Configuration protection

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

Configuration read-only mode applies only to the CLB console. You can still modify configurations through API operations.

Console

Go to the Instances page of the CLB console, click the ID of the target instance to go to the Instance Details page. In the Basic Information section, turn on or turn off the Deletion Protection and Configuration Read-only Mode switches.

API

Idle instances

Release idle instances promptly to better manage costs.

  • A pay-as-you-go CLB instance is idle if it has not been used for more than 7 consecutive days and meets any of the following conditions:

    • The instance is in the Stopped state.

    • No listeners are 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 set to 0.

  • Idle instances still incur fees. A CLB instance incurs fees until it is released.

Console

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

  2. In the upper-right corner of the idle instance list, click Settings to customize displayed columns, such as IP Address, Region, and Cause of Idleness.

  3. Confirm the instance is not in use and no longer needed, then click Release in the Actions column.

Resource cleanup

  • Prerequisites

    • You cannot release an instance for which deletion protection is enabled. If you call the DeleteLoadBalancer API with deletion protection enabled, the call returns the error code OperationDenied.DeleteProtectionIsOn. To release the instance, go to the Instance Details page and turn off the Deletion Protection switch. Then retry the release.

    • If a CLB instance is managed by another Alibaba Cloud service (such as Container Service for Kubernetes, ACK), the instance cannot be manually released from the console. To release a managed instance, find and delete the associated managed resources (for example, delete the corresponding Kubernetes Service). The CLB instance is automatically released after the managed resources are deleted.

    • If the elastic IP address (EIP) or Internet Shared Bandwidth instance associated with a CLB instance is in the financial lock state (locked due to overdue payment), the CLB instance cannot be released. To resolve this, renew your account to remove the financial lock on the associated resources, and then retry the release.

    • If the EIP or Internet Shared Bandwidth instance associated with a CLB instance has already been released by the system due to overdue payment, the CLB instance may enter a residual locked (unavailable) state. In this case, you can directly release the unavailable CLB instance.

    • You can release only pay-as-you-go instances.

    • Subscription instances: These instances are automatically released upon expiration and cannot be manually released. If required, go to the Unsubscribe management center to request a self-service unsubscription.

      • Instances in the expired-and-stopped state are automatically released after the expiration date.

      • Instances in the financial lock state (due to overdue payment) must be renewed to remove the lock before any operations can be performed.

      Subscription CLB instances are no longer available for purchase since December 1, 2024. Renewals will be discontinued starting December 1, 2026. Before your renewal expires, you can choose to renew or switch to the pay-as-you-go billing method. For more information, see End of sale for CLB subscription instances.

  • Release methods

    • You can select Release Now or Scheduled Release based on your business requirements. If you select scheduled release, the system stops billing at the specified time and releases the instance at the next hour.

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

      • You can bind a retained EIP to other instances in the same region. This allows you to use the same public IP address when you migrate instances.

        When you perform this operation for the first time, the system automatically creates a service-linked role named AliyunServiceRoleForSlbEipAccess to allow CLB to access EIPs.

      • A retained EIP is billed separately. By default, the EIP is a pay-as-you-go resource that is billed based on data transfer. The default maximum bandwidth is 200 Mbit/s.

  • Impacts

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

    • Releasing a CLB instance does not affect running backend servers.

    Warning

    • If you mapped a custom domain name to the IP address of a CLB instance, change the DNS record to point to another load balancer instance before you release the CLB instance to prevent service interruptions.

    • If you plan to point the domain name directly to an ECS instance after decommissioning the CLB instance, ensure the following before releasing the CLB instance:

      • The ECS instance has a public IP address or an EIP configured for Internet access.

      • Your application has been deployed on the ECS instance and verified to work correctly.

      • Update the DNS A record to point to the ECS public IP address.

      • Verify that your application is accessible through the new DNS resolution.

      • If you also use Auto Scaling (ESS), disable the scaling group during off-peak hours to avoid impacting running instances.

    • After a CLB instance is released, all configurations and data associated with the instance will be deleted and cannot be recovered.

    • If your CLB instance is managed by another Alibaba Cloud service such as Container Service for Kubernetes (ACK), releasing the CLB instance will disrupt the related service. This action is irreversible.

Troubleshoot instance release issues

If you are unable to release a CLB instance, identify the cause from the following scenarios and follow the corresponding resolution steps.

Deletion protection

When deletion protection is enabled, the Release Settings button in the instance list is grayed out and cannot be clicked.

To resolve this issue:

  1. Click the instance ID to go to the Instance Details page.

  2. In the Basic Information section, turn off the Deletion Protection switch.

  3. Return to the instance list and retry the release operation.

Managed instances

If a CLB instance is managed by another Alibaba Cloud service (such as Container Service for Kubernetes (ACK) or Flink), the instance cannot be manually released from the CLB console.

  • ACK-managed instances — Delete the corresponding Kubernetes Service in ACK. The CLB instance is automatically released after the managed resources are deleted.

Subscription instances

Subscription CLB instances cannot be manually released and are automatically released upon expiration. If you need to release a subscription instance before it expires, go to the Unsubscribe management center to request self-service unsubscription.

If the instance is in the financial lock state due to overdue payment, renew it to remove the lock before submitting an unsubscription request.

Console

  1. Go to the Instances page of the CLB console. In the Actions column of the target instance, choose More Actions > Release Settings.

  2. Select a Release. When you release an Internet-facing IPv4 CLB instance, you can select Convert to EIP and Retain the IP.

API

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

Billing

Newly purchased CLB instances support only the pay-as-you-go billing method.

Effective 00:00:00 (UTC+8) on January 1, 2026, Alibaba Cloud will stop selling CLB instances that are billed by specification.

  • Internet-facing CLB instance: Fees include instance fees, public IP retention fees, LCU fees, and data transfer fees.

  • Internal CLB instance: Fees include instance fees and LCU fees. If you bind an EIP, the EIP is billed separately.

Quotas

Resource

Default quota

Increase quota

CLB instances per Alibaba Cloud account

60

To increase this quota:

Related topics

  • Server groups: Groups of backend servers that receive requests from a CLB instance.

  • Listeners: Check for connection requests and distribute them to backend servers based on the configured scheduling algorithm.

  • Configure a domain name: Map a custom domain name to the CLB service IP address so clients can access services through the domain name.

FAQ

Does CLB offer a free trial?

CLB does not provide a dedicated free trial entry. You can directly create a pay-as-you-go CLB instance to try it out. Billing for a pay-as-you-go instance starts as soon as the instance is created. Release the instance promptly after you finish testing.

How do I stop traffic to a CLB instance or confirm there is no traffic before releasing it?

Stop traffic

Use either of the following methods to stop service traffic to a CLB instance:

  • Remove or pause the DNS records that point to the CLB instance IP address.

  • Stop the corresponding listener in the listener list of the CLB instance to stop accepting new connections.

Verify that there is no traffic

TCP listeners forward data packets transparently by default, so monitoring data may include non-service traffic such as internet scanning. To avoid accidental service interruptions, follow these steps:

  1. Pause (rather than directly delete) the DNS records and observe for 24 hours to confirm that no normal service access requests are received.

  2. After confirming there is no traffic, delete the DNS records and release the CLB instance to avoid service interruption caused by accidental deletion.

Pre-release check

Before releasing the instance, confirm that the CLB instance is not managed or depended on by the following cloud services. Otherwise, releasing it may cause the associated service to malfunction:

  • Container Service for Kubernetes (ACK): If the CLB instance is created by an ACK Service, delete the corresponding Service in the ACK cluster first. The CLB instance is then released automatically.

  • WAF: If the CLB instance is associated with WAF protection, remove the association before releasing the CLB instance.

I received a notification about an unreleased free or idle CLB instance, but I cannot find it in the console. What should I do?

If you receive an SMS or internal message stating that your account has an unreleased free or idle CLB instance, but you cannot find the instance after logging on to the console, troubleshoot as follows:

  1. Confirm that you have logged on to the console with the Alibaba Cloud account specified in the notification. This avoids querying the wrong scope due to multiple accounts.

  2. On the Instances page of the CLB console, switch to the region specified in the notification and check the instance list in that region. Instances are isolated by region, so check each region one by one.

  3. If you cannot find the instance in any region, check the Idle Instances page under your account, or contact technical support for further assistance.

Will adjusting listener configurations or replacing backend servers change the CLB instance IP address?

No. The public or private IP address of a CLB instance remains unchanged throughout the instance lifecycle. Adjusting listener rules or replacing backend servers does not affect the service endpoint. As long as the CLB instance is not released, its IP address remains valid.

The IP address in the DNS record does not match the actual CLB IP address, causing access failures. What do I do?

Troubleshoot as follows:

  1. On the Instances page, confirm the actual IP address of the CLB instance in the Endpoint column.

  2. Check the DNS records of the domain name and confirm that the IP address that the A record (or AAAA record) points to matches the CLB instance IP address.

  3. If you have updated the DNS record, changes may take from several minutes to several hours to propagate due to ISP LocalDNS caching. Wait for the cache to expire before testing, or use nslookup or dig against a public DNS server (such as 8.8.8.8) to verify the resolution result.

  4. Check and align the DNS records for both the primary domain name and subdomains (such as www.example.com and example.com) so that they all point to the same correct CLB instance IP address. If access fails because you accidentally deleted the A record for the primary domain name, re-add the corresponding A record to restore access.

How do I determine whether a specific IP address belongs to my CLB instance?

The service endpoint of a CLB instance is displayed in the Endpoint column on the Instances page of the CLB console. To determine ownership:

  • If the IP address appears in the Endpoint column of a CLB instance under your account, the IP address belongs to that CLB instance.

  • If the IP address falls within a common private CIDR block (such as 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16) but does not appear in the CLB instance list, it is not a CLB-specific address and may belong to another resource in the VPC.

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