Advanced → RTP sets the UDP port range that Asterisk uses for the audio and video of calls (RTP). The firewall of PhonixPBX opens this range automatically.
Click Save and then apply the changes, see Applying changes.
Port range
| Field | Meaning | Default |
|---|---|---|
| First port | First UDP port of the range, 1024–65535. | 10000 |
| Last port | Last UDP port of the range, 1024–65535. It must be greater than the first port. | 20000 |
Each call uses two ports per call leg; a call between a phone and a provider has two legs. The default range of 10 000 ports is enough for any realistic load. Make the range smaller only when a router or firewall in front of the PBX requires it, and keep at least a few hundred ports.
Behind a NAT router, forward exactly this UDP range to the PBX, together with the SIP port (see NAT). A missing forward typically results in calls without audio or with audio in one direction only.