Locate the response family
- 1xx ProvisionalRequest is progressing180 belongs here
- 2xx SuccessRequest succeeded
- 3xx RedirectionAnother destination
- 4xx Request failureInterpret this request
- 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
The receiving side reports that alerting is being attempted. This is normal provisional signaling and is not a final answer.
Read it in context
A caller may hear locally generated ringback while a downstream endpoint alerts. The sound heard by the caller does not establish that a specific physical handset rang; intermediaries and alternate destinations can influence the flow.
Administrator checks
Trace the selected destination and identify the source of 180. If the intended desk stays silent, inspect routing, forwarding, do-not-disturb and the endpoint response. Compare the PBX call record with the handset history.
Next action and common mistake
Do not troubleshoot established-call audio solely from ringback. If the call answers and then has silence, follow the accepted SDP and RTP path. Treat unanswered timeout handling as a separate business routing decision.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.