This topic describes the regions and zones that support Classic Load Balancer (CLB).

Regions and zones

A region is a group of Alibaba Cloud data centers deployed within a geographical location. After you create a resource, you cannot change the region to which the resource belongs. Each region consists of one or more zones with independent power supplies and network infrastructure. If one of the zones in a region is down, the other zones can still serve your workloads. Regions are independent of each other. Zones are isolated from each other. Connections between zones within the same region provide low network latency.

Classic Load Balancer (CLB) supports cross-zone deployment in most regions. You can deploy a CLB instance across zones within the same region to achieve zone-disaster recovery and improve service stability and reliability. When the primary zone is down, Classic Load Balancer (CLB) fails over to the secondary zone within about 30 seconds. When the primary zone recovers, Classic Load Balancer (CLB) automatically fails back to the primary zone.

Before you deploy a Classic Load Balancer (CLB) instance across zones, take note of the following items:

  • Elastic Compute Service (ECS) instances added to a Classic Load Balancer (CLB) instance are deployed across the primary and secondary zones. Before you add ECS instances to a Classic Load Balancer (CLB) instance, you need only to make sure that the ECS instances and the CLB instance belong to the same region. Classic Load Balancer (CLB) distributes network traffic to ECS instances across zones.
  • By default, if the primary zone of a Classic Load Balancer (CLB) instance is active, the CLB instance does not distribute network traffic from the secondary zone. You cannot manually configure the Classic Load Balancer (CLB) instance to distribute network traffic from the secondary zone. The CLB instance switches network traffic to the secondary zone only when the primary zone is down. For example, when the primary zone is down due to power outages or fiber cuts, the secondary zone of the Classic Load Balancer (CLB) instance automatically takes over. An unhealthy ECS instance does not trigger a zone failover.
  • ECS instances are independent from Classic Load Balancer (CLB). If the primary zone of Classic Load Balancer (CLB) is down, the ECS instances may still provide services. For example, when Zone A of Classic Load Balancer (CLB) is down, the secondary zone of Classic Load Balancer (CLB) takes over. Classic Load Balancer (CLB) can distribute network traffic across the ECS instances that are deployed in different zones. However, if the whole zone is down due to power outages or fiber cuts, all resources in this zone stop running, including the Classic Load Balancer (CLB) instance and the ECS instances.

Regions and zones that support IPv4 CLB instances

Region Primary zone
China (Qingdao) Zone B and Zone C
China (Beijing) Zone A, Zone D, Zone E, Zone G, Zone H
China (Zhangjiakou) Zone A and Zone B
China (Hohhot) Zone A and Zone B
China (Hangzhou) Zone B, Zone D, Zone E, Zone F, Zone H and Zone I
China (Shanghai) Zone A, Zone B, Zone C, Zone D, Zone E, Zone F, Zone G, Zone L
China (Shenzhen) Zone A, Zone B, Zone C, Zone D, Zone E
China (Heyuan) Zone A and Zone B
China (Chengdu) Zone A
China (Hong Kong) Zone B, Zone C, and Zone D
Philippines (Manila) Zone A
Japan (Tokyo) Zone A and Zone B
Singapore (Singapore) Zone A, Zone B, and Zone C
Indonesia (Jakarta) Zone A, Zone B, and Zone C
Australia (Sydney) Zone A and Zone B
Malaysia (Kuala Lumpur) Zone A and Zone B
India (Mumbai) Zone A and Zone B
South Korea (Seoul) Zone A
Thailand (Bangkok) Zone A
US (Silicon Valley) Zone A and Zone B
US (Virginia) Zone A and Zone B
Germany (Frankfurt) Zone A, Zone B and Zone C
UK (London) Zone A and Zone B
UAE (Dubai) Zone A
Note

Classic Load Balancer (CLB) instances in the South Korea (Seoul) and Thailand (Bangkok) region support only Layer 4 load balancing.

Regions and zones that support IPv6 CLB instances

Table 1. Regions and zones that support IPv6 CLB instances on Alibaba Cloud
Region Zone
China (Qingdao) Zone B and Zone C
China (Beijing) Zone A, Zone D, Zone E, Zone G, and Zone H
China (Zhangjiakou) Zone A and Zone B
China (Hohhot) Zone A and Zone B
China (Hangzhou) Zone B, Zone D, Zone E, Zone F, Zone H, and Zone I
China (Shanghai) Zone A, Zone B, Zone C, Zone D, Zone E, Zone F, Zone G, and Zone L
China (Shenzhen) Zone A, Zone B, Zone C, Zone D, and Zone E
China (Heyuan) Zone A and Zone B
China (Chengdu) Zone A
China (Hong Kong) Zone B, Zone C, and Zone D
Singapore Zone A, Zone B, and Zone C
US (Virginia) Zone A and Zone B
Germany (Frankfurt) Zone A and Zone B

References