What are some of the symptoms of SIP ALG?

There are many symptoms of SIP ALG, here are some of the most common ones.

  • One-way or no-way audio, intermittently or consistently
  • Outbound or Inbound call fails to connect.
  • Audio cuts out completely while on a call and unable to traverse.
  • Phones continue ringing and unable to answer
  • Unable to call other extensions in your company's network
  • BLF or MWI are being sent to an incorrect extension, behaving slow, or does not work at all.

What do I need to do next?

It is easy to detect SIP ALG presence but not so much in turning it off if not supported.  Some tips are as follow;

  • SIP ALG is sometimes referred to as SIP Transformation,  SIP Helper, SIP Guide and etc..
  • SIP ALG is not always available in the GUI of the device administration page.  You may have to contact the vendor or SSH/Telnet into it to do so ( if supported )
  • SIP ALG is maybe turned on in some Modem devices.   If this is the case, ensure that it is set to bridge mode.  ( if supported )
  • In some cases, SIP ALG can not be turned off as it is not supported by your device.   This is when you should consider getting an alternative device.
  • If a PE ( customer provider ) device is installed in your Demarc and you have no access to it, you may have to contact the ISP provider to disable SIP ALG.

We have compiled a list of  known router issues which you can use to see if your router/firewall is on the list.