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The Draytek Vigor series of ADSL routers have a feature known as a SIP Application Level Gateway (ALG).

This ALG has some bugs that makes it incompatible with the Wi-Manx ADSL service. The ALG on the Draytek router can be disabled as follows;

  • Update the firmware to the latest version (see
  • Telnet to the router’s IP address
  • Enter the router admin password
  • Enter the following command “sys sip_alg 0″
  • This will disable the ALG on the Draytek and make the VoIP service function as normal