@otoh wrote:
I have internal (on the same network as the PBX) and external (via NAT) phones. A recent change in routers required some changes to get my external phones working. I got it running but am prompted to try to understand how RTP ports work/are agreed on...
Previous Netgear router worked well, no problem with external phones:
- Yealink phones have default RTP range 11780-11800
- Router forwarding ports 10000-20000
- FreePBX RTP ports default 10000-20000
Switching to a Draytek:
- No change to phone ports
- Router set up in the same way as before, 10000-20000
- No audio on FreePBX - but fixed when set the RTP ports to match the phone ports, 11780-11800
This prompts various questions:
- Which end decides which RTP ports to use? This suggests that FreePBX was using ports from the larger range, which were not accepted by the phone
- In which case, how/why did it work with the previous router?
- How many RTP ports are needed per call - by setting FreePBX to this smaller range, am I limiting how many calls it will handle?
Any help in understanding much appreciated!
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