Two CompletePBX servers comprise an Active/Passive cluster where one of the servers acts as the Master server and the other server acts as the Slave (hot-backup) server. Each server has its own private IP address. This allows server management and configuration replication to be performed between the two servers via the IP network. The VoIP PBX extensions communicate with the PBX cluster via a special public (or cluster) IP address, which is activated only on the current Master server.
When the servers swap roles, due to the Master server failure, for example, then that cluster IP address will be activated automatically on the Slave server. As a result, the IP phones will continue to use the same PBX IP address.
If the TwinStar Plus mechanism detects a problem with the function of the primary server, it immediately passes control to the backup server. All telephony lines are automatically recognized and activated by the backup server, and all communication in the organization is re-established within minutes.