SIP 401 Unauthorized
KamailioRFC 3261 §22.1The server is challenging the request for digest authentication. This is normal on the first INVITE / REGISTER and almost never indicates an issue on its own — but a *loop* of 401s usually does.
Common causes on Kamailio
- Wrong SIP password or username casing
- Authentication realm mismatch
- Auth header reused after `nonce` expired
- PBX expecting MD5 vs SHA-256 (depending on RFC 8760 support)
Stop guessing — paste your trace
Drop your PCAP or sngrep log and SIP Flow will render the ladder, surface the failing transaction, and (optionally) ask Gemini to suggest the fix grounded in Kamailio docs.
Open analyzerDon't have a trace yet? See how to capture one in Wireshark, sngrep, or your PBX