Virtual IP Address Overview

What Is a Virtual IP Address?

A virtual IP address can be shared among multiple ECSs. An ECS can have a private and a virtual IP address, which allows your users to access the ECS through either IP address.

You can use either IP address to enable layer 2 and layer 3 communications in a VPC, access a different VPC using peering connections, and access cloud servers through EIPs.

You can bind a virtual IP address to ECSs deployed in the active/standby pair, and then bind an EIP to the virtual IP address. Virtual IP addresses can work together with Keepalived to ensure high availability and disaster recovery. If the active ECS is faulty, the standby ECS automatically takes over services from the active one.

Networking

Virtual IP addresses are used for high availability and can work together with Keepalived to make active/standby ECS switchover possible. This way if one ECS goes down for some reason, the other one can take over and services continue uninterrupted. ECSs can be configured for HA or as load balancing clusters.

• Networking mode 1: HA

  To improve service availability and eliminate single points of failure, you can deploy ECSs in the active/standby pair or deploy one active ECS and multiple standby ECSs. And then, you can bind the same virtual IP address to these ECSs. If the active ECS becomes faulty, a standby ECS takes over services from the active ECS and services continue uninterrupted.

  Figure 1 Networking diagram of the HA mode
  
  • As shown in the above figure, bind a virtual IP address to two ECSs in the same subnet.
  • Configure Keepalived for the two ECSs to work in the active/standby pair. Follow industry standards for configuring Keepalived. The details are not included here.

Application Scenarios

• Accessing the virtual IP address through an EIP

  If your application has high availability requirements and needs to provide services through the Internet, it is recommended that you bind an EIP to a virtual IP address.

• Using a VPC peering connection to access a virtual IP address

  To ensure high availability and access to the Internet, use a VPC peering connection to ensure that two VPCs in the same region can communicate with each other.

Notes and Constraints

• Virtual IP addresses are not recommended when multiple NICs in the same subnet are configured on an ECS. Using the virtual IP addresses may cause route conflicts on the ECS, which would lead to communication failures.
• If a virtual IP address is used in an active/standby scenario, disable IP forwarding on the standby ECS. For details, see Disabling IP Forwarding on the Standby ECS.