A high-availability virtual IP address (HAVIP) is a private IP address that can be created and released as an independent resource. You can use HAVIPs with high-availability (HA) software such as Keepalived to deploy services in active/standby mode. This improves the availability of your services.

ECS/ENI

Feature and supported regions

The HAVIP feature is in public preview. To use this feature, submit a ticket.

The HAVIP feature is free of charge during the public preview. After the public preview ends, you are charged for using HAVIPs. For more information, see Alibaba Cloud official announcements. Alibaba Cloud does not provide service level agreement (SLA) guarantees during the public preview.

The following table describes the regions that support HAVIPs.
Area Region
Asia Pacific 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), Japan (Tokyo), Singapore (Singapore), Australia (Sydney), Malaysia (Kuala Lumpur), and Indonesia (Jakarta)
Europe & Americas US (Silicon Valley), US (Virginia), Germany (Frankfurt), and UK (London)
Middle East & India India (Mumbai) and UAE (Dubai)

Feature overview

Each Elastic Compute Service (ECS) instance is assigned a private IP address as the primary IP address. You can associate HAVIPs with an ECS instance to increase the number of private IP addresses available for the ECS instance. Both the primary IP address and HAVIPs of an ECS instance can be used to establish connections. In addition, you can use HAVIPs with HA software such as Keepalived to deploy services in active/standby mode. This improves the availability of your services. For more information, see Implement active/standby high availability by using HAVIPs and keepalived. You can associate an HAVIP with ECS instances by using the following methods:
  • Directly associate an HAVIP with ECS instances.

    Each HAVIP can be associated with two ECS instances. After an HAVIP is associated with ECS instances, the ECS instances can send Address Resolution Protocol (ARP) messages to advertise the HAVIP. After the ECS instances advertise the HAVIP, one of the ECS instances serves as the primary instance, and the other ECS instance serves as the secondary instance. If the primary ECS instance is down, the secondary ECS instance takes over to provide services.

  • Associate an HAVIP with the primary elastic network interfaces (ENIs) of the ECS instances or the secondary ENIs of the ECS instances.

    Each HAVIP can be associated with the primary ENIs or secondary ENIs of two ECS instances. After an HAVIP is associated with the ENIs, the ENIs can send ARP messages to advertise the HAVIP. After the ENIs advertise the HAVIP, one of the ENIs serves as the primary ENI, and the other ENI serves as the secondary ENI. If the primary ENI is down, the secondary ENI can take over to provide services.

HAVIPs have the following features:
  • HAVIPs are floating private IP addresses and are not statically assigned to ECS instances or ENIs. HAVIPs can be associated with or disassociated from ECS instances or ENIs through ARP advertisement.
  • You must associate HAVIPs with ECS instances or ENIs within the same vSwitch. This means that the ECS instances or ENIs must belong to the same subnet.
  • You can associate each HAVIP with two ECS instances or two ENIs. However, you cannot associate an HAVIP with an ECS instance and an ENI at the same time.

Scenarios

HAVIPs support flexible configurations in the following scenarios:
  • Scenario 1: Internal-facing HA services

    In the following figure, two ECS instances are assigned the same HAVIP. Keepalived is configured for the ECS instances to provide an internal-facing HA service. Other instances in the same virtual private cloud (VPC) can access this service. The HAVIP serves as the service address. If the primary ECS instance is down, the secondary ECS instance takes over. This improves the availability of your services.

    Scenario 1
  • Scenario 2: Internet-facing HA services

    In the following figure, two ECS instances are assigned the same HAVIP. Keepalived is configured and the HAVIP is associated with an elastic IP address (EIP) for the ECS instances to provide an Internet-facing HA service. The EIP that is associated with the HAVIP serves as the service address. If the primary ECS instance is down, the secondary ECS instance takes over. This improves the availability of your services.

    Scenario 2

Limits

Before you use HAVIPs, take note of the following limits:
Item Default limit Adjustable
Network types that support HAVIPs VPCs N/A
Maximum number of HAVIPs that can be associated with each ECS instance 5
Maximum number of ECS instances or ENIs that can be associated with each HAVIP 2
Whether HAVIPs support broadcasting or multicasting Not supported
Note HAVIPs support only unicasting. To implement high availability through third-party software such as keepalived, you must modify the configuration file to change the communication method to unicasting.
Maximum number of HAVIPs that can be created with each account 5

Go to the Quota Management page to increase the quota. For more information, see Manage resource quotas.

Maximum number of HAVIPs that can be created in each VPC 5
Maximum number of route entries that point to an HAVIP in each VPC 5

Use HAVIPs

For more information, see Implement active/standby high availability by using HAVIPs and keepalived.