Hello, I think the point ist that you use the IP of your proxy as the realm instead of your domain in X-Lite. You can see it in the call-ID in your messages: -------------------- SEND >> 192.168.1.2:5060 REGISTER sip:192.168.1.2 SIP/2.0 Via: SIP/2.0/UDP 192.168.1.203:5060 From: <sip:1000@192.168.1.2> To: <sip:1000@192.168.1.2> Contact: "JesusR" <sip:1000@192.168.1.203:5060> Call-ID: 854E48C84C104A5DB92CE4A65ABC2406(a)192.168.1.2 CSeq: 31483 REGISTER Expires: 500 User-Agent: X-Lite build 1016 Content-Length: 0 ----------------------- Notice the call-id is xxxx(a)192.168.1.2 but not xxxx(a)voztelecom.net. However, in the 401-challenge which you received the realm is "voztelecom.net": ---------- WWW-Authenticate: Digest algorithm=MD5,nonce="3f1c562000000000dded3e97ed7f89d3722ff12d3704a884",realm ="voztelecom.net" ------------- I think you should change your realm in X-Lite from 192.168.1.2 to voztelecom.net and everything will be ok. Otherwise, the X-Lite will treat the 401 response as an illegal challenge and won't send back his credential. Best regards yang