Knowledge Base

Disabling SIP ALG on a Thomson Router


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 Thomson router. SIP ALG on this router is known to cause problems with VoIP calls. Proceed as follows:

  1. Open Command Prompt – “Start” → “Run” → type “cmd” and press “Enter”.
  2. In Command Prompt, type “telnet” and press enter. is the default IP address of the router. If you are running on Windows 7/8/8.1/10, you might need to install the telnet client from “Control Panel” → “Programs and Features” → “Turn Windows features on and off”.
  3. The default username is “Administrator”, and there is no default password, leave blank.
  4. Type “connection unbind application=SIP port=5060” and press “Enter”.
  5. Type “saveall” and press “Enter”.
  6. Type “exit” and press “Enter” to exit the telnet session.

SIP ALG in now disabled on your Thomson router.


  • The SIP phones behind this router should be configured not to use STUN
  • The SIP phones must NOT be configured with a local port of 5060 or 5061. The local port of the phone must be changed to something else.
  • Configuring a SIP Phone behind a Thomson router might require port forwarding to be implemented on the router. So you will need to port forward the SIP and AUDIO (RTP) ports on the thomson router and point them to the SIP Phone’s IP Address.