You can create IPv6 Classic Load Balancer (CLB) instances. After you create an IPv6 CLB instance, the system allocates a public IPv6 address to the CLB instance. The public IPv6 address is used to receive requests from IPv6 clients.

Background information

IPv6 is short for Internet Protocol Version 6. IPv6 is the next-generation Internet Protocol (IP) designed by Internet Engineering Task Force (IETF) to replace IPv4, which is the current version of IP. IPv6 extends the length of an IPv4 address from 32 bits to 128 bits. This means that the address space is expanded to 2^96 times the original size. Therefore, IPv6 ensures that each instance can be allocated an IP address.

Regions and zones that support IPv6 CLB instances

Table 1. Regions and zones that support IPv6 CLB instances on Alibaba Cloud
Region Zone
China (Beijing) Zone A, Zone B, Zone C, Zone D, Zone E, Zone F, Zone G, Zone H, Zone I, Zone J, and Zone K
China (Zhangjiakou) Zone A, Zone B, and Zone C
China (Hohhot) Zone A and Zone B
China (Ulanqab) Zone A, Zone B, and Zone C
China (Hangzhou) Zone B, Zone D, Zone E, Zone F, Zone G, Zone H, and Zone I
China (Shanghai) Zone D and Zone E
China (Shenzhen) Zone A, Zone B, Zone C, Zone D, Zone E, and Zone F
China (Guangzhou) Zone A and Zone B
China (Chengdu) Zone A and Zone B
China (Hong Kong) Zone B, Zone C, and Zone D
Singapore (Singapore) Zone A, Zone B, and Zone C
US (Virginia) Zone A and Zone B
Germany (Frankfurt) Zone A and Zone B
Table 2. Regions and zones that support IPv6 CLB instances on Finance Cloud
Region Zone
China (Hangzhou) Zone I and Zone H
China (Shanghai) Zone G and Zone F
China (Shenzhen) Zone A, Zone B, Zone C, Zone D, Zone E, and Zone F
Table 3. Regions and zones that support IPv6 CLB instances on Alibaba Gov Cloud
Region Zone
China (Beijing) Zone A, Zone B, Zone C, and Zone D

Features of IPv6 CLB instances

  • Switching from IPv4 to IPv6 without negative impacts on your business
    • You can add IPv4 Elastic Compute Service (ECS) instances to an IPv6 CLB instance to receive IPv6 requests without the need to modify your business system.
    • When your existing IPv4 CLB instances are unable to withstand the growing user traffic, you can create IPv6 CLB instances. This way, clients can access your CLB instances by using IPv4 or IPv6. In addition, this does not adversely affect your business system.
  • More secure and reliable workload deployment
    • You can configure a blacklist for CLB to block network traffic from malicious IP addresses.
    • You can also configure a whitelist for CLB to allow network traffic only from specified IP addresses.

Limits

  • The IPv6 network environment of Alibaba Cloud is in the initial stage of development. If you cannot connect to an IPv6 service, submit a ticket for technical support. Alibaba Cloud does not provide service level agreement (SLA) guarantees during the public preview.
  • IPv6 packets have longer IP headers than IPv4 packets. When an IPv6 CLB instance uses a UDP listener, make sure that the following requirement is met: The maximum transmission unit (MTU) supported by the elastic network interface (ENI) that each backend server uses to communicate with CLB does not exceed 1,200 bytes. Otherwise, oversized packets may be discarded. You must modify the MTU settings in the configuration files of some applications accordingly. TCP supports the Maximum Segment Size (MSS) announcement. Therefore, you do not need to modify the configurations of applications if a CLB instance uses a TCP listener.
  • HTTP listeners can use the X-Forwarded-For header field to obtain IPv6 addresses of clients.