NLB instance

DNS name

Each NLB instance is assigned a DNS name. To use a custom domain, create a CNAME record pointing to the NLB DNS name.

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 locked, an instance 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 between public and private by changing the network type.

Feature	Public NLB instance	Private NLB instance
Scenarios	Exposes backend services to the internet.	Serves internal traffic within a VPC only.
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
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 access the instance over IPv4 only (for example, 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 access the instance over IPv4 (for example, 192.168.0.1) or IPv6 (for example, 2001:db8:1:1:1:1:1:1).

The network type of a dual-stack instance is determined by its IPv4 address: private IPv4 = private instance, public IPv4 = public instance.

Dual-stack is available for new instances only. Existing IPv4 instances cannot be upgraded to dual-stack.

Regions that support dual-stack NLB instances

Public cloud regions

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), China (Nanjing-Local Region) (being decommissioned), China (Wuhan-Local Region), and China (Fuzhou-Local Region) (being decommissioned)
Asia Pacific	Thailand (Bangkok), Philippines (Manila), Singapore, Japan (Tokyo), South Korea (Seoul), Malaysia (Kuala Lumpur), and Indonesia (Jakarta)
Europe and Americas	Germany (Frankfurt), UK (London), France (Paris), US (Virginia), US (Silicon Valley), and Mexico

Finance Cloud regions

Area	Region
China	China East 1 Finance, China North 2 Finance (invitation-only preview), China East 2 Finance, China South 1 Finance

Government Cloud regions

Area	Region
China	China North 2 Alibaba Gov. Cloud 1

Cross-zone load balancing

NLB distributes traffic through VIPs across multiple zones for zone-level high availability. The cross-AZ forwarding feature routes traffic to backend servers in other zones. Enabled by default, you can disable cross-AZ forwarding to reduce forwarding latency.

Traffic distribution example

An NLB instance distributes traffic to two ECS instances in Zone A and eight in Zone B. DNS distributes traffic evenly between zones (50% each). The backend scheduling algorithm 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%.