This topic describes the regions and zones supported by Classic Load Balancer (CLB).
Regions and zones
A region is a geographical area where data centers are located. After you create a resource, you cannot change its region. A zone is a physical area within a region that has independent power and network infrastructure.
Zones within the same region are interconnected through a low-latency internal network. Zones are designed for fault isolation. If one zone fails, it does not affect the normal operation of other zones. Each region is completely independent, and zones in different regions are isolated.
To provide a stable and reliable load balancing service, Classic Load Balancer (CLB) is deployed across multiple zones in most regions for intra-region disaster recovery. If the primary zone becomes unavailable, CLB can fail over to a secondary zone in about 30 seconds to restore service. When the primary zone recovers, CLB automatically fails back to the primary zone.
Note the following about the primary and secondary zones of a Classic Load Balancer (CLB) instance:
You can add backend ECS instances from different zones to a Classic Load Balancer (CLB) instance, as long as the ECS instances and the CLB instance are in the same region. The CLB instance can distribute traffic to ECS instances across multiple zones.
Under normal circumstances, the Classic Load Balancer (CLB) instance in the secondary zone is in a standby state. You cannot manually switch the active/standby status of a Classic Load Balancer (CLB) instance. The Classic Load Balancer (CLB) fails over to the secondary zone only when Alibaba Cloud detects that an entire zone is unavailable, for example, due to a complete data center power outage or a fiber optic cable cut. A failover is not triggered by the failure of a single instance.
CLB and ECS instances are deployed in separate clusters. For example, if a CLB in Zone A becomes unavailable, the ECS instances in the same zone are not necessarily unavailable. Therefore, if a CLB failover is caused only by a CLB cluster failure, the CLB in the secondary zone can still distribute traffic to ECS instances in different zones. However, if all clusters in an entire zone experience a power outage or a fiber cut, all services in the zone, including but not limited to CLB and ECS, will become unavailable.
Supported regions and zones
The regions and zones in the following tables are for reference. For the most current availability, refer to the buy page.
Area | Region | Zone |
China | China (Hangzhou) | Zone B, Zone D, Zone E, Zone F, Zone G, Zone H, Zone I, Zone J, and Zone K |
China (Shanghai) | Zone A, Zone B, Zone C, Zone D, Zone E, Zone F, Zone G, Zone L, Zone M, Zone N, and Zone O | |
China (Shenzhen) | Zone B, Zone C, Zone D, Zone E, and Zone F. Zone F is a secondary zone and is not supported as a primary zone. | |
China (Heyuan) | Zone A, Zone B, and Zone C | |
China (Guangzhou) | Zone A and Zone B | |
China (Qingdao) | Zone B and Zone C | |
China (Beijing) | Zone A, Zone D, Zone E, Zone G, Zone H, Zone I, Zone J, Zone K, and Zone L | |
China (Zhangjiakou) | Zone A, Zone B, and Zone C. Zone C is a secondary zone and is not supported as a primary zone. | |
China (Hohhot) | Zone A and Zone B | |
China (Ulanqab) | Zone A, Zone B, Zone C, and Zone D | |
China (Chengdu) | Zone A, Zone B, and Zone C. Zone B is a secondary zone and is not supported as a primary zone. | |
China (Zhongwei) | Zone A and Zone B | |
China (Hong Kong) | Zone B, Zone C, and Zone D | |
Asia Pacific | Philippines (Manila) | Zone A and Zone B |
Thailand (Bangkok) | Zone A and Zone B | |
Singapore | Zone A, Zone B, and Zone C | |
Japan (Tokyo) | Zone A, Zone B, Zone C, Zone D, and Zone E | |
South Korea (Seoul) | Zone A and Zone B | |
Malaysia (Kuala Lumpur) | Zone A, Zone B, and Zone C | |
Malaysia (Johor) | Zone A and Zone B | |
Indonesia (Jakarta) | Zone A, Zone B, and Zone C | |
Europe and Americas | Germany (Frankfurt) | Zone A, Zone B, and Zone C |
UK (London) | Zone A and Zone B | |
US (Virginia) | Zone A and Zone B | |
US (Silicon Valley) | Zone A and Zone B | |
Mexico | Zone A and Zone B | |
France (Paris) | Zone A and Zone B | |
Middle East | UAE (Dubai) | Zone A and Zone B |
SAU (Riyadh - Partner Region) | Zone A and Zone B |
Classic Load Balancer (CLB) instances in the Thailand (Bangkok), SAU (Riyadh - Partner Region), and Mexico regions support only Layer 4 capabilities.
Supported regions for IPv6 CLB
Area | Region |
China | China (Qingdao), China (Beijing), China (Zhangjiakou), China (Hohhot), China (Ulanqab), China (Hangzhou), China (Shanghai), China (Shenzhen), China (Heyuan), China (Guangzhou), China (Chengdu), China (Hong Kong) |
Asia Pacific | Singapore |
Europe and Americas | US (Virginia) and Germany (Frankfurt) |
Middle East | SAU (Riyadh - Partner Region) |
Classic Load Balancer (CLB) instances in the SAU (Riyadh - Partner Region) region support only Layer 4 capabilities.
Only Internet-facing Classic Load Balancer (CLB) instances support IPv6.
Related APIs
DescribeRegions: Queries the available regions.
DescribeZones: Queries the zones in a specified region.