All Products
Search

This Product

    Server Load Balancer:NLB instance

    Document Center

    Server Load Balancer:NLB instance

    Last Updated:May 15, 2026

    An NLB instance receives requests from clients and forwards them to backend servers based on listener configurations.

    DNS name

    An NLB instance provides services through a DNS name. To access the instance using a custom domain name, you can create a CNAME record that maps your domain to the DNS name of the NLB instance.

    Load balancer domain names have been upgraded. New NLB instances cannot be accessed directly using their DNS names.

    Instance status

    Status

    Description

    Lock type

    Deletable

    Modifiable

    Running

    The instance is working properly.

    Not applicable

    • No (if deletion protection is enabled)

    • Yes (if deletion protection is disabled)

    • No (if modification protection is enabled)

    • Yes (if modification protection is disabled)

    Creating

    The instance is being created.

    No

    No

    Updating

    The instance configuration is being updated.

    No

    CreateFailed

    Instance creation failed.

    Yes

    Stopped

    When an instance is locked for a specific reason, it enters the Stopped state and becomes unavailable.

    Locked for overdue payment : The instance is locked due to an overdue payment. Renew your subscription to unlock the instance and resume service.

    No

    Locked due to associated resource : The associated EIP or Shared Bandwidth instance is locked due to an overdue payment . Renew the subscription for the associated resource to unlock the instance and resume service.

    No

    Locked due to residual dependency: The associated EIP or Shared Bandwidth instance was released due to an overdue payment. The current instance is unavailable. You must release the instance.

    Yes

    Security-locked: The instance is locked for security reasons. Go to the Security Control page to request an unlock.

    No

    Instance network type

    You can switch an NLB instance between public and private network types by changing the network type.

    Feature

    Public NLB instance

    Private NLB instance

    Scenarios

    Use a public NLB instance to expose backend services to the internet.

    Use a private NLB instance for services accessible only from within an Alibaba Cloud VPC.

    IP address allocation

    Assigns an EIP and a private IP address.

    You can bind an Anycast EIP to an NLB instance to provide low-latency access for services across multiple regions.

    Assigns only a private IP address.

    Access mode

    Accessible from the internet and from within a VPC.

    Accessible only from within a VPC.

    Logic diagram

    		 image image

    Billing

    Includes the instance fee, LCU fee, and public network fee (for the EIP).

    Includes only the instance fee and LCU fee.

    Protocol version

    Protocol version

    Default IP allocation (per AZ)

    Description

    IPv4

    • public IPv4 instance: one public IPv4 address and one private IPv4 address.

    • private IPv4 instance: one private IPv4 address.

    Clients can only access the instance using an IPv4 address, such as 192.168.0.1.

    dual-stack

    • public dual-stack instance: one public IPv4 address, one private IPv4 address, and one IPv6 address.

    • private dual-stack instance: one private IPv4 address and one IPv6 address.

    Clients can access the instance using an IPv4 address (for example, 192.168.0.1) or an IPv6 address (for example, 2001:db8:1:1:1:1:1:1).
    The network type of a dual-stack NLB instance is determined by its IPv4 address. If the instance has a private IPv4 address, it is a private instance. If the instance has a public IPv4 address, it is a public instance.
    You can only create new dual-stack instances. You cannot upgrade an existing IPv4 instance to a dual-stack instance.

    Regions that support dual-stack NLB instances

    Area

    Region

    China

    China (Hangzhou), China (Beijing), China (Shenzhen), China (Shanghai), China (Qingdao), China (Zhangjiakou), China (Chengdu), China (Guangzhou), China (Hong Kong), China (Heyuan), and China (Ulanqab)

    Asia Pacific

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

    Europe & Americas

    Germany (Frankfurt), UK (London), France (Paris), US (Virginia), US (Silicon Valley), and Mexico

    Middle East

    Saudi Arabia (Riyadh)

    Cross-zone load balancing

    An NLB instance forwards traffic through VIPs in multiple availability zones to achieve zone-level high availability. The cross-AZ forwarding feature allows a VIP to forward traffic to backend servers in other availability zones. This feature is enabled by default. You can disable cross-AZ forwarding to reduce network forwarding latency.

    Traffic distribution example

    An NLB instance forwards traffic through VIPs to two backend ECS instances in Availability Zone A and eight backend ECS instances in Availability Zone B. The DNS algorithm evenly distributes traffic between the two availability zones (50% each). The scheduling algorithm for backend servers is round-robin.

    If cross-AZ forwarding is enabled:

    • All 10 ECS instances share the traffic load equally, each receiving 10% of the traffic.

    If cross-AZ forwarding is disabled:

    • Availability Zone A: The two ECS instances in this zone share 50% of the traffic, each receiving 25%.

    • Availability Zone B: The eight ECS instances in this zone share 50% of the traffic, each receiving 6.25%.
    image image