Frequently Asked Questions

What is NAT ALG and how does it affect VOIP call issues?

Even though SIP ALG is intended to assist users who have phones on private IP addresses, in many cases it is implemented poorly and actually causes more problems than it solves. SIP ALG modifies SIP packets in unexpected ways, corrupting them and making them unreadable. This can give you unexpected behavior, such as phones not registering and incoming calls failing.

Therefore if you are experiencing problems we recommend that you check your router settings and turn SIP ALG off if it is enabled.

Symptoms:
•One-way audio when first picking up a phone call.
•Dead air/dropped calls when first picking up a phone call.
•Cannot hear party at other end when first picking up a phone call.
•Only 1 phone in a hunt group with multiple phones is ringing

NAT ALG is typically in the on default position on most internet routers.

To test if ALG is active on your network router, download this quick tool.
Download Here (Must be run within the local network)

How do I turn off SIP ALG (Application Layer Gateway)?

The method to disable SIP ALG will depend on your router. Please check your routers administrative instructions for directions or contact AV LinkPro support for instructions for a specific router or internet gateway (modem).

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Last Updated a year ago