Statisches Port mapping im HideNat
Im HideNat sollte es die Möglichkeit geben die Ports im HideNat statisch zu setzen, dies ist vorallem für Telefonanlagen wichtig, dass die RTP Ports statisch sind und dem Quellport entsprechen
John Lebherz kommentierte
Auszug aus dem 3CX Manual
If you are using a VoIP provider, you will need to have a firewall that supports and is configured to use static port mapping. Static port mapping is required for RTP, the protocol that carries audio, to be able to function correctly.
VoIP applications that use the RTP protocol to send and receive audio and video streams, tend to have problems behind a firewall or a router since RTP uses random ports to send and receive audio or video streams. Incorrect firewall configuration will cause calls made via a VoIP providers or to remote extensions to have no audio or one way audio only.
When using Symmetric NAT, the firewall/router will change the port on which the audio is received, on the fly. For example, when making an outbound call via a VoIP provider, 3CX Phone system will make a STUN resolution to determine the public IP and port to use. It will then specify this to the other party. Meanwhile, the firewall will close the port specified in the INVITE, causing the call to fail. Obviously there is no way a VoIP call can be established reliably if the firewall does this. This procedure is called Symmetric NAT and must be switched off.