http://www.3cx.com/blog/docs/disable-sip-alg-on-fortigate/How to Disable SIP ALG on Fortinet / FortiGateBy Andreas Psyllos, Google+ profile Posted on : October 12, 2012, Last modified on : June 05, 2014

SIP ALG is used to try and avoid configuring Static NAT on a router. Its implementation, however, varies from router to router, often making it difficult to inter-operate a router with SIP ALG enabled with a PBX. In general, you would want to disable SIP ALG and configure one to one port mapping on the router.In this article, we will show you how to disable SIP ALG on FortiGate. On devices running FortiOs, you will need to disable this in multiple places as shown below.1. Open the Fortigate CLI from the dashboard.2. Enter the following commands in FortiGates CLI: 1. config system settings2. set sip-helper disable3. set sip-nat-trace disable4. reboot the device3. Reopen CLI and enter the following commands do not enter the text after //: 1. config system session-helper2. show //locate the SIP entry, usually 12, but can vary.3. delete 12 //or the number that you identified from the previous command.4. Disable RTP processing as follows: 1. config voip profile2. edit default3. config sip4. set rtp disableThere might be other settings that you need to configure depending on the FortiOS version that you are using. If you continue encountering issues related to SIP ALG, please contact Fortinet Support.Further Information Procedure to troubleshoot a remote extension Documentation on FortiGates SIP Inspection features