This is a classic NAT problem, and is due to the fact that your telephone does not have a "real" IP address.

If you are located behind a router or a firewall, and you have problems, please note the following:

Typical errors that can be caused by your router / firewall are:

• You cannot be contacted from an external location.
• A ringing tone can be heard at the remote site, but you are unable to hear any speech.
• Ringing continues at the called party, although you have already hung up.
• The call is disrupted after 6-12 seconds.
• You can dial a number, but you cannot hear a ringing tone.
• It is not possible to hold a conversation when the call is answered.

These errors cannot always be reproduced and sometimes only occur after hours or days. In many cases, you can resolve these problems by means of a firmware update to the router. Please contact your router manufacturer in this regard.

If the problem persists, activate the transfer of the following ports to your router/firewall:

Standard:
Port: 5060 / UDP (SIP signalling)
Port: 5004 / UDP (RTP, voice)
Port: 3478 UDP (STUN)

X-Lite:
Port 5060 / UDP
Port 8000 - 8019 / UDP
Port 3478 /UDP

In addition: UPnP

If your router supports UPnP (Universal Plug and Play), it could be helpful as a final step to activate / deactivate this option.

If these measures are unsuccessful, you still have an option to use our STUN server. To do so, enter "stun.sipkom.com" as the STUN server.