A high-availability virtual IP address (HAVIP) is a private IP address that can be created and released as an independent resource. After you associate an HAVIP with an Elastic Compute Service (ECS) instance, the ECS instance can advertise the HAVIP by sending Address Resolution Protocol (ARP) messages.

Note 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, fees are incurred. For more information, see Alibaba Cloud official announcements.
  • Alibaba Cloud does not provide any Service Level Agreement (SLA) guarantees for services in public preview.
PrivateLink architecture

Features

After you associate an HAVIP with an ECS instance, the ECS instance can advertise the HAVIP by sending ARP messages. In high-availability (HA) deployment scenarios such as keepalived, HAVIPs allow you to switch from the primary ECS instance to the secondary ECS instance. This improves the availability of your service.

HAVIPs have the following features:
  • An HAVIP is an unfixed private IP address. An HAVIP can be associated with or disassociated from an ECS instance through ARP announcements.
  • An HAVIP can be associated only with the ECS instances that are associated with the same VSwitch. Each HAVIP can be associated with two ECS instances.
  • Each HAVIP can be associated with two ECS instances and one elastic IP address (EIP). After you associate an HAVIP with two ECS instances and one EIP, you can access the ECS instance over the Internet. By default, the primary ECS instance is accessed. If the primary ECS instance is faulty, the secondary ECS instance takes over. This improves the availability of your service.
  • Each ECS instance can claim more than one private IP address by advertising multiple HAVIPs.

Scenarios

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

    In the following figure, keepalived integrates the HAVIP and two ECS instances into a private network-facing HA service. The cloud instances in the same VPC network can access this service over the private network. The IP address of the HAVIP functions as the service endpoint. If the primary ECS instance is faulty, the secondary ECS instance takes over. This improves the availability of your service.

    Scenario 1
  • Scenario 2: Internet-facing HA services

    In the following figure, the HAVIP is associated with two ECS instances and one EIP based on keepalived. You can access the service over the Internet. The IP address of the HAVIP functions as the service endpoint. If the primary ECS instance is faulty, the secondary ECS instance takes over. This improves the availability of your service.

    Scenario 2

Limits

Before you use HAVIPs, note the following limits:
Item Default limit Quota increase
Network types that support HAVIPs VPC type N/A
Number of HAVIPs that can be created under each account 5
Number of HAVIPs that can be created in each VPC 5
Number of HAVIPs that can be associated with each ECS instance 5
Number of ECS instances that can be associated with each HAVIP 2
Number of route entries destined for an HAVIP in each VPC 5
Whether HAVIPs support broadcast or multicast communication Not supported.
Note HAVIPs support only unicast. To implement high availability through third-party software such keepalived, you must modify the configuration file to change the communication method to unicast.

Use HAVIPs

For more information, see Implement high availability through HAVIPs and keepalived.