What is Virtual IP Address

Virtual IP Address (VIP) is an Intranet IP address assigned from a subnet that is not assigned to the Real ECS NIC. VIP has the same network access capabilities as private IP address, and users can access ECS through VIP just like the primary private IP address.

You can bind the virtual IP address to an active/standby ECS, or bind an elastic IP to the virtual IP address based on whether you need to access the Internet, and use it with HA software (e.g. Keepalived) to achieve high service availability.

Note: If it is not used in combination with Keepalived, please be careful to delete the standby server or NIC bound to the virtual IP address, which may cause traffic congestion on the standby server or NIC.

Features

Virtual IP addresses have the following network features:

· The virtual IP address can be dynamically landed on a certain cloud server, which can declare the relationship with it and change the bound server object through the ARP protocol.

· Virtual IP address is an IP address assigned from a subnet, which only supports binding resources that belong to the same subnet.

Networking

Virtual IP address is mainly used with high-availability software (e.g. Keepalived) for the active/standby switchover of ECSs. When the standby server fails, the virtual IP address is dynamically switched to the standby server, which takes over the services of the standby server to ensure normal service operation.

Examples of high availability scenarios: To achieve high service availability and avoid single point of failure, you can use the same virtual IP address and different ECSs to implement the scenario of "one active and multiple standby". When the active server fails, the standby one will become the active server and continue to provide services.

In the "one active and one standby" scenario, the following configurations are required to achieve high availability:

· Bind a virtual IP address to two ECSs that belong to the same subnet.

· Use two ECSs in conjunction with Keepalived and dynamically specify one of them as the active server and the other as the standby server. For details, see Combining Virtual IP address with keepalived to implement high availability in Active/Standby mode.

Scenarios

Combining elastic IP access to Internet services

· When you need to provide high available services, you can bind the elastic IP to virtual IP address to implement high availability over the Internet.

High-availability Intranet services in the cloud

· When you need cloud servers within the same subnet to access highly available services through the same Intranet address, you can bind virtual IP address to the cloud server to implement the scenario of "one active and multiple standby".

Limitations

· Virtual IP addresses can only be bound to servers in the same subnet;

· A virtual IP address can only be bound to one EIP;

· It is recommended that the number of virtual IP addresses bound to a cloud server/physical server should not exceed 10;

· IPv6 type virtual IP does not support binding elastic IP, if you need to access Internet, please add the virtual IP address in the shared bandwidth interface.

For details, see Virtual Private Cloud (VPC) - Virtual IP Address.