Troubleshooting One-Way Audio

Check the Phone Where the Issue is Occurring:

1. When placing or receiving a call, ensure that the call is established. 
   • A good indicator of this is the call timer that appears on the screen.
      
2. Verify that the handset is connected to the correct port on the phone. 
   • The correct port is marked with a picture of a handset.
      
3. Try using the speakerphone to rule out the handset or the handset cord.
    

Network Issues that Usually Cause this Problem:

• Faulty NAT (Network Address Translation) or double NAT (Two routers both supplying NAT);
   
• Firewall Settings preventing RTP or SIP traffic from traveling to the correct destination.
   
• Issues with network switching equipment or physical cabling issues.

Correcting One-Way Audio

1. Start by connecting the phone directly to the router/modem or use the same connection and cabling as a working phone at your location.
    
2. Make a test call to see if the issue still exists.
    
3. Check with whoever services your network and internet connection, such as your IT vendor or ISP to ensure…
   • SPI (Stateful Packet Inspection) and SIP/VoIP ALG (SIP Transformations) are disabled. 
     • We recommend having your IT team or Internet Service Provider (ISP) adjust these settings in the network equipment. 
        
   • Check the quality of your internet connection at https://speed.cloudflare.com/. 
     • If you notice your speeds are being throttled or the Jitter is measuring above 30 ms, then we recommend contacting your Internet Service Provider or IT team to further diagnose any issues on your network. 
        
   • Have your IT team or ISP check your bandwidth management to ensure the IP phones are receiving a robust enough connection to reliably handle calls. 
      
   • Your router may be able to prioritize SIP (IP Phone) traffic. Have your IT staff or vendor configure the Quality of Service on your router.