What is Double Natting?

What is Double Natting?

Network address translation (NAT) is a function that your router or gateway performs to create your network. Double NAT occurs when you connect your router to an ISP gateway or another router
Double-natting is a very common problem with the SIP protocol where the incoming packets do not reach your device, causing no incoming audio. In some cases, the packets from the device also do not reach the other side, causing the other side not to hear anything or issues with internal calls.

The main culprit is the way NAT networks (like your typical home or office router) distribute one internet connection to multiple PC's and phones. To make this possible, they use a method called port mapping.

Without going into details (you can read more here on this), it causes the ports used by VoIP programs to change in a mostly unpredictable way and can often result in one-way or no audio, failed incoming calls, automatic hangup after 30s and more, challenges with transfers and internal calls.

How to check Double Natting The simplest way is to do a traceroute….

On Windows:

Open the Command Prompt (CMD)

Do a traceroute e.g. tracert google.co.za

If the first 2 hops are of the local IP addresses then there is double natting

If the first 2 hops are of the local IP addresses then there is double natting

In a Mac Book

Open the Terminal

Do the traceroute

  • Also, you can try to remove the second router or switch, etc, and test
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