Failover VoIP cluster 3CX

The failover cluster 3CX is a two replicated server PBX. When the primary server fails, the server replica server is activated, minimizing the time that the telephony fails. In this article, we will look at how to correctly configure the fault tolerance of the PBX 3CX.


To use fault tolerance, you need one Enterprise (ENT) or Professional (PRO) license. The ENT license sets the TTL time of the A-record of the FQDN of the 3CX server in 5 minutes. In the PRO TTL license A-record is set to 6 hours. This means that in the PRO edition, the time of emergency reconnection of IP phones, 3CX, 3CX SBC clients and the web client will be much higher.

Implementation of fault tolerance

3CX uses the principle of an active-passive cluster with configuration replication every 24 hours at least. The main (active) node performs VoIP call processing, and the standby (passive) node monitors the active host. If an active host fails (regardless of the reason), the passive host is turned on from about the same state. The mechanism for determining the failure of an active host depends on the settings on the passive host and is discussed below. Powershell failover scripts for Active Directory ), Run with certain privileges.
By default, scripts that can be executed during the backup switch process are executed with the privileges of the 3CX Event Notification Manager service (by default Local System). As a rule, you need DNS server management privileges to run the script (dnscmd or psexec).
Failover VoIP cluster 3CX  
Click on the service in the appropriate Windows snap-in and on the Log On tab, change the account from Local System to the one that has the appropriate privileges to configure DNS, and restart the service. It is recommended that you create an individual user with this privilege and give him an unchangeable password.
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