I use a ZyXEL modem and my calls drop out at 5 minutes?

  1. Click the Start button > Select Run
  2. Type: 
     telnet 192.168.1.1
  3. When asked for Password type 1234 press enter
  4. Select “System Maintenance” by typing 24 then press enter
  5. Select “Command Interface” by typing 8 then press enter
  6. At the prompt, 
     type ip nat service sip active 0
  7. At the prompt type: 
     exit
  8. Select “Exit” by typing 99 then press enter