NAT Port Translation Failure (Symmetric NAT)

Understand NAT port translation failures with symmetric NAT and explore solutions to improve connectivity in your network.

Table of Contents

What does Symmetric NAT mean?

What does Symmetric NAT mean?

For VoIP audio to work correctly, your router must use "Port Preservation" (Consistent NAT). If your router uses "Symmetric NAT" or randomizes the ports it assigns to outbound traffic, Agilico Connect will struggle to establish a stable audio stream, resulting in dead air.

How to fix it:

  1. Disable Symmetric NAT: Log into your router's administrative interface and look for NAT settings. Ensure it is set to "Endpoint Independent", "Full Cone", or "Consistent NAT" rather than "Symmetric" or "Port Randomization".
     
  2. Enterprise Firewalls: If using SonicWall, Fortinet, or WatchGuard, you must configure a specific outbound NAT policy for the device/subnet to retain port preservation for UDP traffic.
     
  3. Firmware Updates: Ensure your router is running the latest firmware, as older consumer routers sometimes have bugged NAT tables.