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.