Connection & Firewall Issues


More often than not, the phone should operate without issue when connected to the Internet via broadband. This section lists some potential problems and gives some debugging hints.

No DHCP Server: Almost all business and home networks now use DHCP, allowing the phone to automatically be assigned a private IP address. If for some reason DHCP is not available at a location, the phone will not be able to initialize. This can be worked around manually but is difficult.

Ports Blocked: Some businesses, and some commercial firewalls installed in homes, block certain ports. A network administrator can be contacted to unblock ports.

  • Port 80 is almost never blocked; that is the port that is used for Web browsing, and the phone uses this port for the dashboard. Messages use HTTP over TCP.
  • Port 5060 is used for Session Initiation Protocol (SIP); this is how the phone sets up and receives call control messages. These messages use UDP.
  • Ports 10000 through 20000 are used for RTP packets; these are the actual voice signals to and from the phone. RTP uses UDP. (The phone uses its own ports 2222 through 2268 for RTP.)
  • Port 53 is used to perform Domain Name System look-ups using DNS over UDP.
  • Port 123 is used to perform Simple Network Time Protocol queries using SNTP over UDP.
  • NAT: Network Address Translation is the standard method for translating between private networks (inside the home or business) and the public Internet. ZipDX automatically supports the most common NAT configurations.

Bandwidth and Prioritization: The phone will be sharing the available Internet bandwidth with anything else connected to the network. When a phone call is active, about 90Kbps is required in each direction to carry the voice packets (whether the phone is operating in HDVoice or in conventional narrowband mode). This is generally not a problem unless the bandwidth of the connection is fairly low (some residential services have low capacity from the home to the network; perhaps as low as ~200Kbps).

Router Issues: Some home routers are known to have issues with the SIP protocol. Apparently the vendors were trying to “improve” operation, but they ended up breaking things. Issues have been observed with certain firmware versions of the very popular Linksys WRT54G, and certain Netgear models.


The phone takes a few minutes to boot. When it is done, it should show a display with the user’s name. Press the HDVoice button to hear the demo. If that works, everything should be operational. Otherwise, follow these steps:

Does the phone show the user’s name? If not, it means something isn’t right with basic network access (or, if something has been misconfigured in ZipDX, an appropriate message will be displayed). Reboot the phone and watch the messages carefully.

If the user’s name is displayed, it means the network connection is good and Port 80 is working. Look at the little spider icon in the very upper left corner of the display, next to “ZipDX”. If it is just an outline, it means port 5060 (SIP) is not working. Contact a network administrator to have this port enabled in the router/firewall.

If the icon is solid black, it means the phone has successfully registered with ZipDX; port 5060 (SIP) is working. Try the HDVoice demo. If the call timer on the display does not start ticking, it means that the call control connection is not being completed. This is probably a firmware issue in the router. See if it is possible to have the user connect using a different router (perhaps at a different location), or if they are technically adept, they can download new firmware from their router vendor’s web site.

If the call timer is ticking but no audio can be heard, it means that the RTP ports are probably blocked. Contact the network administrator about opening ports 2222 through 2268.

If audio is heard but sounds crackly or otherwise impaired, there is probably a bandwidth problem. Ask the user to disconnect other computers from the network, or have them find an alternate Internet connection.



If you have Power-over-Ethernet, the phone can be connected directly to the Network Jack with an Ethernet cable. Otherwise, you will use the Power Insertion cable as shown below. The SoundStation IP-6000 is shown in this example.