If you have a SonicWall firewall, you may be encountering one of two scenarios.

• Consistently relayed connections (blue icon)
• Direct connection (green icon) at first, then switching to a relayed connection shortly thereafter

This can be remedied by enabling a SonicWall feature called Consistent NAT. Consistent NAT enhances standard NAT policy to provide greater compatibility with peer-to-peer applications that require a consistent IP address to connect to.

This setting is usually located under SonicWall VOIP settings