Who this is for: Anyone using a mobile hotspot, cellular router, fixed wireless, or satellite internet for Cannon VoIP desk phones or the app.
What goes wrong
- One-way audio, or no audio, on some calls.
- Incoming calls don't ring until the phone makes an outgoing call.
- Calls drop after a few minutes.
Why it happens
Many cellular and some fixed wireless or satellite services share one public internet address among many customers. This is called carrier-grade NAT (CGNAT). It's a layer of NAT you can't control, on top of your own router.
Those shared systems often forget idle traffic quickly and limit how call traffic comes back in, much like double NAT with short timeouts.
How to fix it
- Use the Cannon VoIP app on a hotspot where you can. The app is built to handle strict networks and uses our relay server (turn.cannonvoip.com) when needed.
- For desk phones on a cellular or similar connection, ask your provider if they offer a public IP address or static IP address. That removes the shared layer.
- If not, make sure your own router is set up well: SIP ALG off and UDP timeouts at 300 seconds or more.
- Make sure the ports on the firewall page aren't blocked by the hotspot or cellular router.
- Use cellular or hotspot internet as a backup, not the main connection for an office full of phones, when you can.
Notes for common router types
- On most cellular routers and hotspots, check the admin page for a SIP ALG or VoIP setting and turn it off, and look for a public IP or IP passthrough option.
- To tell if you're behind CGNAT, compare your router's internet (WAN) address with what a "what is my IP" website shows. If they're different, or the router's address starts with 100.64 to 100.127, you're behind carrier-grade NAT.
How to tell it worked
- Calls on the hotspot or cellular connection have audio both ways.
- Incoming calls ring without anyone making an outgoing call first.
- Run the free Net Checker on that connection.
Still having trouble? Contact Cannon VoIP support at 888-973-0515 or support@cannonvoip.com.
More router settings that affect call quality
- Turn Off SIP ALG
- Set UDP Timeouts to at Least 300 Seconds
- Allow Cannon VoIP Through Your Firewall
- Fix Double NAT (Two Routers in a Row)
- Prioritize Voice Traffic with QoS
- Fix Bufferbloat with Smart Queue Management
- Stop Wi-Fi Band Steering and Roaming from Dropping Calls
- Guest and Isolated Wi-Fi Blocking the App
- DNS and Content Filtering Blocking Cannon VoIP
- VPNs and Security Software Interfering with Calls
- Mesh Wi-Fi Systems and Calls Cutting Out
- Wi-Fi Power Saving Causing Missed Calls
See all router settings · What makes call quality good or bad