SIP ALG is used to try and avoid configuring Static NAT on a router. Its implementation, however, varies from one router to another, 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 a Thompson router. SIP ALG on this router is known to cause problems with VoIP calls. Proceed as follows:
- Open Command Prompt (Start Run type ‘cmd’ and Press Enter).
- In Command Prompt, type ‘telnet 192.168.1.254′ and press enter. 192.168.1.254 is the default IP address of the router. If you are running on Windows 7, you might need to install the telnet client from Control Panel → Programs and Features→ Turn Windows features on and off.
- The default username is ‘Administrator’, and there is no default password so leave the field blank.
- Type ‘connection unbind application=SIP port=5060′ and press Enter.
- Type ‘saveall’ and press Enter.
- Finally type ‘exit’ and press Enter to exit the telnet session.
You have now disabled SIP ALG on your Thompson router.