What SIP 403, 480, 401 and 503 responses mean on a wholesale voice trunk, how to tell whether the problem is your switch, your account or the route, and what to send support.
A SIP error code tells you who refused the call and roughly why. 401 means authentication, 403 means the call was refused, 480 means the destination or route was temporarily not reachable, and 503 means a server or route was unavailable.
| Code | Meaning | Usually check |
|---|---|---|
| 401 / 407 | Authentication required | Username, password, auth settings |
| 403 | Forbidden | Source IP, balance, number format, route |
| 404 | Not found | Number format |
| 480 | Temporarily unavailable | Destination or route, try again later |
| 486 | Busy | Called party busy |
| 503 | Service unavailable | Route capacity — see SIP 503 guide |
+ or 00, plus the route prefix if you use one.480 means the call reached the route but the destination could not be reached at that moment. Retry later or try another route. Repeated 480s on one destination are worth reporting.
To get a fast answer, send in a ticket:
With this we can find the exact call in our records and tell you where it was refused.
Related: Asterisk PJSIP setup, SIP trunk security.
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