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SIP registration troubleshooting
Registration tells a SIP service where a user agent can be reached. A successful registration does not prove that inbound calls or RTP media will work.
Diagnostic sequence
- Confirm the device has an IP address, gateway, DNS, and correct time.
- Resolve the registrar hostname from the device network.
- Check the transport and port in the device configuration.
- Follow the
REGISTER, challenge, authenticated retry, and final response. - Check the expiry and whether NAT bindings remain open long enough.
- Test inbound calling separately from registration.
Common responses
| Response | Likely meaning |
|---|---|
| 401 | Authentication challenge or incorrect credentials on retry |
| 403 | Account, source address, realm, or policy rejected |
| 404 | Registrar or user does not exist at that route |
| 408 | Registrar could not be reached in time |
| 423 | Requested registration expiry is too short |
| 480 | Service or endpoint temporarily unavailable |
Related: DNS and SRV records, NAT troubleshooting, and SIP headers.