We are currently evaluating an integration with a telecom provider (MTN Ghana) that offers SIP trunk services. Before implementation, we would like to confirm the architecture. Can Vapi act as the SIP endpoint for a third-party telecom SIP trunk (for example, from a carrier such as MTN), allowing inbound calls from the carrier to be delivered directly into Vapi voice agents? Or is an intermediary PBX/SIP server such as Asterisk or FreePBX required between the telecom provider and Vapi? We are trying to determine the recommended production architecture before proceeding with the carrier integration.

Hi Adom, Yes, Vapi can act as the SIP endpoint directly. No intermediary PBX (Asterisk, FreePBX, etc.) is required.

Yes, Vapi can act as the direct SIP endpoint — it has its own SBC (Session Border Controller) nodes, so MTN just needs to point inbound calls to Vapi's SIP URI (sip.vapi.ai) and whitelist Vapi's signalling IPs. (Vapi) No Asterisk or FreePBX needed in the middle. The key on MTN's side is making sure they forward calls to the correct SIP URI format and that Vapi's IPs are properly whitelisted — skipping that step is usually what causes 401 unauthorized errors on first setup. (Vapi) One thing worth confirming early: does MTN Ghana support credential-based auth (username/password) or are they expecting pure IP authentication? Vapi actually recommends against IP-only auth on shared infrastructure since it can cause misrouted calls. ( @Adom Isaac