Hey everyone, I’m trying to set up Custom SIP with Vapi, but I’m stuck on the Asterisk configuration side. In another provider we use , they expose a register-less flow: we initiate the call via API, they return a LiveKit address, and we connect directly. Super straightforward. With Vapi, I’m able to start the call via the API, but I can’t figure out what exact Asterisk config is expected for Custom SIP: Do we need to register anywhere, or is it supposed to work fully register-less? Does Vapi send an INVITE to our Asterisk server, or are we supposed to originate the call from our side? What should our pjsip.conf / extensions.conf look like for the inbound leg? Is there a minimal working config you recommend for custom SIP setups? Basically, I need to know the correct Asterisk setup so that API-initiated calls from Vapi can reach our server. Any help or sample config would be hugely appreciated. 🙏

Hi emre, If you need help with setting up SIP trunking for your Vapi integration, I can guide you through the process for various providers like Plivo, Twilio, and others. For a complete setup, you'll generally need to: 1. **Choose Your SIP Provider**: Ensure your provider is supported by Vapi. Supported providers include Plivo, Twilio, Telnyx, Zadarma, or a custom "BYO" SIP Trunk. Each has a slightly different setup, outlined in our [SIP Trunking Guide](https://docs.vapi.ai/advanced/sip/sip-trunk). 2. **Configure Your Provider**: - **Plivo**: Add IP addresses to Plivo's IP Access Control List and create outbound and inbound trunks. - **Twilio**: Create an Elastic SIP Trunk and set up termination and origination for inbound and outbound calls. 3. **Authenticate via API**: - Use Vapi API to create SIP trunk credentials with your provider’s details. The API also helps register your phone numbers with these credentials for proper routing. 4. **Make and Test Calls**: - Using Vapi's API or dashboard, link your phone numbers to the SIP trunk and test outbound calls. - Ensure all IPs are properly allowlisted to avoid unauthorized errors. For specific steps related to your provider, kindly refer to the detailed guide provided in our [documentation](https://docs.vapi.ai/advanced/sip). If you have any provider specifications you're currently stuck on, let me know, and I can help you further from there.