Dropouts are caused because engin send re-invites every 5 minutes whilst on a call. If the ports are not forwarded, the NAT session times out and the port is closed. Consequently. the re-invite from engin fails and the call is deemed to be finished and it disconnects. (Always check your engin call log and see if they are 5min 32s long)

You will need to telnet into your Billion VoIP modem and change the default register port to another value.

1. Go to start > run
2. Type:strong>

   telnet 192.168.1.254

3. Enter the username: admin and password: admin (default authentication)
4. Type:

   voip endpoint 1 set sip regport 5070

5. Type

   system config save

6. Type:

   user logout