Technical Tip: Configuring FortiGate for 3CX Phone System

kumarh · ‎10-14-2024

Description

This article describes the necessary FortiGate configuration changes for integrating the 3CX Phone System with a network.

Scope

All FortiGate Firmware.

Solution

Traffic flow would be as follows:

Lan-------------Fortigate(wan)-----------3CX services

Step 1: Disable SIP ALG.

config system settings

set default-voip-alg-mode kernel-helper-based

end

Next, remove the session helper:

config system session-helper

show

delete 13

end

Clear the sessions in FortiGate or reboot the device.

Step 2: Create Outbound Rule 3CX, referto the following documents only for outbound policy:

Step 3:

Create a Virtual IP for each 3CX service port and then add this VIP in Inbound rule.

image (7).png

Create the Firewall Policy:

Policy & Objects -> Firewall Policy -> Create New.
Set source, destination (Virtual IPs), and disable NAT.

image (8).png

Step 4: Split DNS for Internal Resolution.

Configure DNS:

Network -> DNS Servers -> Create New.
Set private IP for 3CX server.