Es empfiehlt sich, folgender Anleitung zu folgen: Fortigate

How to disable SIP-ALG (SIP Helper) on Fortinet

Open the Fortigate CLI from the dashboard. Enter the following commands in FortiGate’s CLI config system settings set sip-helper disable set sip-nat-trace disable reboot the device

Reopen the FortiGate CLI and enter the following commands (do not enter the text after //) config system session-helper show // you need to find the entry for SIP, usually 12, but it may vary delete 12 // or the number that you identified from the previous command

FORTIGATE

Create a rule and set it like in the picture above Reboot the device and you should be ready Disable RTP processing as follows

config voip profile edit default config sip set rtp disable

Eine Komplette Anleitung zur VoIP Konfiguration für FortiOS 5.6 finden Sie in diesem Dokument: FortiOS5.6