Hi Vapi Support, We are integrating Netelip DID 34910053XXX via BYO SIP Trunk. Netelip is sending INVITE to: sip:34910053XXX@593c49fd[[hidden]].sip.vapi.ai Vapi responds: SIP/2.0 401 Unauthorized WWW-Authenticate: Digest realm="593c49fd-e3fa-43fe-[[hidden]].sip.vapi.ai", algorithm=MD5, qop="auth", nonce="..." Netelip does NOT resend the INVITE with Authorization (Digest), so the call never establishes and Vapi Call Logs remain empty. Questions: 1) For inbound BYO SIP trunk calls, does Vapi REQUIRE SIP Digest authentication, or can it accept unauthenticated INVITEs based on gateway IP allowlisting? 2) If Digest is required: which username/password should the provider use? - Is it the SIP Trunk "Authentication (Optional)" username/password we set in the Vapi SIP Trunk configuration? 3) Any additional requirements (headers / Request-URI format) beyond: {phone_number}@{credential_id}.sip.vapi.ai and allowlisting Vapi IPs 44.229.228.186/32 and 44.238.177.138/32? We can share full SIP traces (INVITE/401) if needed. Thanks.

For inbound BYO SIP trunk calls, if Digest authentication is required, your provider should use the username and password set in your Vapi SIP trunk configuration. Here’s an example of the relevant section in your Vapi credential setup:

json
"outboundAuthenticationPlan": {
  "authUsername": "YOUR_SIP_NUMBER",
  "authPassword": "YOUR_SIP_PASSWORD"
}

Make sure Netelip uses these credentials when responding to the 401 challenge, and that the INVITE is sent to

{phone_number}@{credential_id}.sip.vapi.ai

with Vapi IPs allowlisted. For more details, see the [Vapi SIP Trunking documentation](https://docs.vapi.ai/advanced/sip/sip-trunk). Source: - [SIP Trunking](https://docs.vapi.ai/advanced/sip/sip-trunk)

Hi, Thank you for reaching out, I will answer your questions one by one, 1. Vapi does not support Digest authentication for inbound calls. The authentication is solely based on IP only. 2. Since Vapi doesnt allow digest authentication, you can skip this 3. Apart from the ones you provided, Make sure you have whitelisted your SIP provider's IP address range on SIP trunk setup on Vapi dashboard.