SIP ALG (Application Layer Gateway) is a feature which is enabled by default in most Technicolor routers and inspects VoIP traffic as it passes through and modifies the messages on-the-fly.

In few situations this is useful, but in most situations SIP ALG can cause problems using the service. Very often, SIP ALG is poorly implemented causing VoIP messages to be modified in a harmful way or simply corrupts them. In such cases you may experience issues registering your handset, one-way or no audio, unable to receive calls, and issues with BLF and Message Waiting Indicators.

For our Hosted VoIP service, including out Single User services, SIP ALG must be disabled on your Technicolor router.

This guide explains how to disable SIP ALG on the following models:

• Technicolor TG589vac
• Technicolor TG589vac v2
• Technicolor TG588v v2

For other Technicolor router models, such as the Technicolor TG582n and Technicolor TG589vn V3, see this guide.

1. Fire up a browser (Firefox, Chrome etc) and go to 192.168.1.1 (this is the default IP address)
2. On the top-right click Sign in
   • The default username is admin and the default password is admin
3. Amend the URL so there is ?debug=1 at the end
   so the URL should be similar to http://192.168.1.254/?debug=1
4. Scroll down and click on NAT Helpers
5. Toggle the switch for SIP to switch it OFF and click Close
6. Close your browser and restart your handset. SIP ALG is now disabled.

Different Technicolor routers may have different instructions. Please see list below for instructions for your particular device.