I configured an SIP Trunking to VAPI, what works perfectly as outbound, but when I call the phone number it does not even ring, it is completely silent. What could be the problem?

Hi there! 👋 I see you're having an issue with inbound calls not ringing on your Telnyx SIP Trunk to VAPI. I'd be happy to help troubleshoot this! I don't have access to your specific configuration details, but I can definitely share some common causes for this issue based on the information I have. Here are several potential reasons why your inbound calls might be silent: 1. **SIP URI Configuration Issues**: According to the [VAPI documentation](https://docs.vapi.ai/advanced/sip/telnyx), the

sipUri

attribute might not be correctly formatted or the Translated Number setting in Telnyx might not match your VAPI SIP URI username. 2. **Network and Firewall Issues**: Firewall settings or SIP ALG (Application Layer Gateway) could be interfering with SIP messages. As mentioned in [troubleshooting documentation](https://discord.com/channels/1211482211119796234/1211483291191083018/threads/1334919245468799007), ensure your firewall is properly configured to allow SIP traffic and that there are no blocks on the ports used by SIP. 3. **PBX Configuration**: Your PBX might not be configured to accept connections from VAPI's IP addresses, or there might be NAT traversal issues preventing SIP messages from reaching your PBX. 4. **SIP REFER Handling**: VAPI uses SIP REFER for call transfers. According to [configuration documentation](https://discord.com/channels/1211482211119796234/1211483291191083018/threads/1336713212233515089), you need to ensure your system is set up to handle these messages. 5. **Telnyx Inbound Configuration**: The Translated Number setting in Telnyx needs to match the username part of your VAPI SIP URI. For example, if your SIP URI is

sip:username@sip.vapi.ai

, the Translated Number should be set to "username" as explained in the [Telnyx integration guide](https://docs.vapi.ai/advanced/sip/telnyx).

For inbound calls, VAPI requires your telephony to send us the authorization header, which includes your username and password. The username has to be your SIP username, and the password can be anything except being empty or whitespace. Can you ask the Telenyx team to share the PCAP file because it contains information about your inbound call that is likely missing, which is causing the call rejection?

What exactly is the username? Is it only the number like 1234567@sip.vapi.ai? And do i have to add the + or not? And the password is only a placeholder that does not have to be configured anywhere?

This ticket has been marked as solved, and as a result, you will no longer receive any further responses. Kindly create a new support ticket to escalate your inquiry.