Applies to VoipNow 3.0.0 and higher!
Sometimes certain calls or phones happen to drop after 30 seconds. Usually it's because signaling (SIP dialog) has not been properly established. Technically, the SIP ACK (Acknowledgement) message does not reach the intended destination within a specific timeout period. This may happen for a lot of reasons and, consequently, there is no straightforward way to fix it. You need to know the SIP protocol, the way in which the call gets established as well as what messages are exchanged between the two parties involved in the call.
Before you start running any checks, you should verify the VoipNow configuration.
As we've already mentioned, there's no easy to fix this, but there are a couple of ways you can figure out what causes the calls to hang up:
Dial *52 and wait for more than 30 seconds.
If the hangup occurs after 30 seconds, the problem is most likely due to the network setup of the registered extension. NAT can also be the cause considering that the phone might send the internal IP as the source. In this case, using stun or disabling SIP ALG on the router that is in front might help.
Sometimes the poorly built firewalls may not allow UDP to pass properly. In this case there are two things you can do:
For example, if the wrong CallerID is sent (e.g if 0003*001), providers might not recognize it as valid. As a result, 30 seconds later, the call will be dropped.
Some specific remote numbers or prefixes can also trigger the hangup because providers might not route the call. If that's the case, you need to check things with the SIP provider.
If you've tried all these methods and none of them has worked, please contact Support.