If your calls are being dropped abruptly after 32 seconds or if you are missing media in one direction (often video), then it is likely that your router is implementing a feature called a SIP-ALG in an erroneous way. Try to login onto your router, look for a tickbox or similar option where you can turn off the SIP-ALG. Sometimes, you will have to look for the latest version of the firmware, upgrade your router for that option to appear.

When placing a box (or a JoicePhone) behind a LinkSys WRT610N router, you are likely to experience problems such as missing media (video) and calls being dropped after 32 seconds. To remedy these problems, you should upgrade to the latest version of the firmware and turn off a feature called SIP-ALG from the web interface.

The ZyZEL router NBG334W implements a SIP-ALG that cannot easily be turned off using the web interface. Fortunately, the router also implements a telnet server via which it is possible to turn off the ALG implementation. This is necessary since the implementation is broken. To turn off, telnet to the device, typically 192.168.0.1 on the default port and using the password that was set to log in via the web server. Note that only one user can be connected to the device at a time, which means that logging in via telnet will kick out the web login, if any.

At the command prompt, you can type ip alg display to get a list of the different ALG that are implemented by the router, including their current status. To turn off the SIP-ALG, enter ip alg disable ALG_SIP. Check it worked using the display command above. Once done, you will be able to use STUN on top of the device.

The Netgear DG384Gv4 is a combo ADSL modem/router that interferes with the transport protocol that is used by Joice boxes and softphones. To resolve communication issues when you own such a modem/router, you should turn off its so-called SIP-ALG. To do this, log into the router's web interface and choose Advanced->WAN setup in the menu to the left. Then make sure the Disabled SIP-ALG is ticked, if not, tick it and save your changes.

Note that some prior versions of the firmware on the router were not able to turn off the SIP-ALG using the procedure described above. In that case, you will have to update your router firmware according to these instructions.

Also note that there are several versions of this router (the v4 at the end of the name, for example). Maybe does your router work as is in an earlier/later version. If so, you could help other users by leaving a comment on this page.