My telephone cannot place or receive calls, or my telephone becomes unregistered periodically.

There are a few common scenarios that will cause any combination of these symptoms. Please see below for instructions on troubleshooting:

1. If telephones register, but then later become unregistered, it is likely that your router device is closing the previously negotiated port translation to keep the session active. To correct this, lower the "expire time" setting on your telephone device. We recommend setting this to 300 seconds (5 minutes). The setting may also be labeled to the effect of "re-register time" on your IP telephone. Additionally, if your telephone supports the use of "NAT keepalive", we recommend turning this setting on.

2. Many routers contain a firewalling technology known as SPI (Stateful Packet Inspection). SPI tries to monitor active "sessions" on a router, and if the router sees traffic that it doesn't believe belongs to an active session, the traffic is blocked. SPI is known not to have a good implementation in dealing with SIP or VoIP, and is most notable on Netgear routers. In any case, if any of the described symptoms occur, we recommend you check your router configuration for SPI and disable this feature.