Locate the response family
- 1xx ProvisionalRequest is progressing
- 2xx SuccessRequest succeeded
- 3xx RedirectionAnother destination
- 4xx Request failureInterpret this request480 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
The addressed user is temporarily unavailable under the recipient’s handling. Availability and routing state need examination; the code is not a hardware diagnosis.
Read it in context
An endpoint may be unregistered or otherwise unavailable, or an intermediary may apply presence or routing policy. A healthy trunk registration does not establish that the final extension is available.
Administrator checks
Check the called identity, current contacts, forwarding and destination state. Determine whether the response came from the endpoint, PBX or carrier. Compare another destination and inspect any supplied retry guidance without assuming it is always present.
Next action and common mistake
Do not replace credentials solely because 480 appeared. Restore the intended availability or route, then test both direct extension calls and public-number delivery. Verify voicemail or overflow behavior when the user remains intentionally unavailable.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.