Locate the response family
- 1xx ProvisionalRequest is progressing
- 2xx SuccessRequest succeeded
- 3xx RedirectionAnother destination
- 4xx Request failureInterpret this request407 belongs here
- 5xx Server failureServer could not fulfil
- 6xx Global failureFailure across destinations
Read the status with its request method and call leg. For example, 200 after REGISTER confirms a binding; it does not prove an INVITE succeeded.
What this response means
A SIP proxy challenges the request for proxy authentication. A challenge followed by a compatible authorized retry can be normal.
Read it in context
An outbound proxy may require credentials distinct from the registrar or public extension identity. A client that responds with the wrong authorization context can remain in a challenge loop even when the secret appears correct elsewhere.
Administrator checks
Inspect Proxy-Authenticate and the following Proxy-Authorization behavior, method and realm. Verify the configured outbound proxy and carrier guide. Compare algorithm capabilities and ensure the request is reaching the intended service.
Next action and common mistake
Do not substitute server-authentication settings blindly or publish full authorization exchanges. Correct the supported proxy relationship and follow the retry to its final result. A normal 407 step is not evidence that RTP, routing or the entire call failed.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.