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NAT Issues

NAT stands for "Network Address Translation"

What is NAT?

It is the process by which your router allows your internal network devices (such as your phones and computers) to talk to external servers and services (such as MaxoTel).

Different router vendors have different implementations of NAT. These can vary between vendors, router models and even firmware versions.

Common NAT Problems

Common issues arising from NAT problems include:

  • One-way audio
  • Phones ring, but no audio (in either direction) when the handset is picked up
  • Unreliable phone registration (phones periodically don't ring for incoming calls, or periodically lose their connection)
  • Random phones (or new phones) added to the network can't connect


NAT issues can often be temporarily alleviated simply by rebooting the router. This will clear the "NAT table" and force the router to re-create its associations between your devices and their external service connections.

This will only provide a temporary solution, as it's very likely that the problem will re-occur again over time.

Troubleshooting Steps:

  • Disable any port forwarding, DMZ or Port triggering rules on the router
  • Change the "Local/Source SIP Port" on your handsets to be a different port on each handset - guides for both Yealink and Grandstream phones are available here: Yealink or Grandstream GRP
  • (where available) Change the "NAT Type" setting on the router - try different available options (Type A, B, etc.)
  • Upgrade the firmware on the router
  • Replace the router with a different / higher capacity model

For more support:

SIP ALG issues can often present with the same symptoms as NAT issues.

Please Contact Us for further assistance with NAT issues.

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