URGENT!! BYO SIP Trunk - 403 Forbidden & Provider Fallback Issue
Configuration Verified
Phone number correctly linked to credential via credentialId
Credential shows as active in GET requests
Gateway IP corrected from DNS lookup to actual signaling IP
Authentication updated via PATCH request
Key Questions
Why is Vapi falling back to vapi.sip instead of using the BYO trunk?
What triggers this fallback?
Is the credential being marked as failed internally?
Can you provide SIP-level diagnostics:
PCAP or SIP trace of authentication attempt
Exact 403 response from provider's server
What From/To headers Vapi sends
Authentication format used (realm/domain?)
How to verify password was saved?
GET requests don't show password (expected)
Is there a validation endpoint?
Inbound routing:
What SIP URI should provider route calls to?
Any specific headers required beyond inboundEnabled: true?
What We Need
SIP trace of call ID 019a1645-fe0c-7662-8c8c-53e411457614
Reason for fallback to vapi.sip provider
Internal credential status - is it marked as failed?
Guidance on resolving 403 authentication issue
Expected vs Actual
Expected:
Calls use BYO SIP trunk at 85.194.242.50:5060
Transport shows byo-sip-trunk
Authentication succeeds
Call completes
Actual:
Vapi falls back to own trunk (vapi.sip)
403 Forbidden error
Call fails in <1 second
Context
15+ working Telnyx BYO numbers in same organization
Issue persists 24+ hours despite multiple fixes
Provider confirms all settings are correct
Request: Please investigate why BYO trunk isn't being used and provide SIP diagnostics to resolve authentication failure.
Phone number correctly linked to credential via credentialId
Credential shows as active in GET requests
Gateway IP corrected from DNS lookup to actual signaling IP
Authentication updated via PATCH request
Key Questions
Why is Vapi falling back to vapi.sip instead of using the BYO trunk?
What triggers this fallback?
Is the credential being marked as failed internally?
Can you provide SIP-level diagnostics:
PCAP or SIP trace of authentication attempt
Exact 403 response from provider's server
What From/To headers Vapi sends
Authentication format used (realm/domain?)
How to verify password was saved?
GET requests don't show password (expected)
Is there a validation endpoint?
Inbound routing:
What SIP URI should provider route calls to?
Any specific headers required beyond inboundEnabled: true?
What We Need
SIP trace of call ID 019a1645-fe0c-7662-8c8c-53e411457614
Reason for fallback to vapi.sip provider
Internal credential status - is it marked as failed?
Guidance on resolving 403 authentication issue
Expected vs Actual
Expected:
Calls use BYO SIP trunk at 85.194.242.50:5060
Transport shows byo-sip-trunk
Authentication succeeds
Call completes
Actual:
Vapi falls back to own trunk (vapi.sip)
403 Forbidden error
Call fails in <1 second
Context
15+ working Telnyx BYO numbers in same organization
Issue persists 24+ hours despite multiple fixes
Provider confirms all settings are correct
Request: Please investigate why BYO trunk isn't being used and provide SIP diagnostics to resolve authentication failure.
