Using VoiceBlue Lite VoIP GSM gateway behind NAT firewall with dynamic IP address

Using VoIP GSM Gateways behind a NAT firewall with a dynamic IP address (typical of ADSL connection) usually means checking the NAT firewall IP address whenever the connection is re-opened.

The VoIP GSM Gateway behind a NAT firewall uses the public IP address of the NAT firewall as a so-called ‘fake' IP address. The VoIP GSM Gateway sends this ‘fake' IP address to a Registrar server while registering or to a SIP proxy when it sends an INVITE packet. If the NAT firewall IP address is changed, the VoIP GSM Gateway sends the ‘fake' IP address in the INVITE packet with a faulty IP address and the Registrar/SIP proxy replies to the faulty IP address, which means that communication is not established.

Therefore, the 2N VoiceBlue Lite VoIP GSM Gateway is capable of using the STUN service for checking its ‘fake' IP address. The STUN server responds to the request generated by 2N VoiceBlue Lite  and its response contains the NAT firewall IP address (‘fake' IP address). It is necessary to provide the STUN server IP address and the time of the next STUN request. 2N VoiceBlue Lite automatically requests for its ‘fake' IP address in regular intervals as defined.  The STUN service uses port no. 3478 and so the NAT firewall should open this port.