Callers hear each other only one way: classic one-way audio.
Signalling runs over SIP, audio over RTP. RTP arrives on a different port than SIP, and NAT or firewall blocks one direction.
Try this first
- 1Open the RTP port range on the firewall toward PBX or phone
- 2Check NAT type on the router, no symmetric NAT
- 3Enable STUN or an SBC on the PBX side
- 4Inspect codec and SDP negotiation in pcap
When to bring us in
Symmetric NAT at a CGNAT provider: ask for a public IP or a full SBC solution, otherwise it stays flaky.
See also
- Voys, BelXS or RoutIT, which cloud PBX fits?Three popular NL platforms, differences are admin UI, partner model and per-user price.
- Teams Phone: Calling Plan, Direct Routing or Operator Connect?Three ways to connect PSTN to Teams, cost and management differ a lot.
- 3CX: self-host on VPS or take 3CX cloud?Self-host saves licence, but you own SBC, backup and updates.
None of the above fits?
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