I have couple f cisco phones 7906 flashed with SIP firmware. They were connected with TB box (asterisk 1.2) and have worked fine. Today I have duplicated TB extension on my elastix (1.5.2) and try to register phones with elastix. No one phone has registered. Asterisk CLI on elastix shows (the same for each phone): avs01*CLI> <--- Transmitting (no NAT) to 10.233.112.104:49157 ---> SIP/2.0 401 Unauthorized Via: SIP/2.0/UDP 10.233.112.104:49157;branch=z9hG4bK56af9061;received=10.233.112.104 From: <sip:email@example.com>;tag=001e4a922caf000be65eaa81-1ee177a1 To: <sip:firstname.lastname@example.org>;tag=as387f0e26 Call-ID: email@example.com CSeq: 110 REGISTER User-Agent: Asterisk PBX Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY Supported: replaces WWW-Authenticate: Digest algorithm=MD5, realm="asterisk", nonce="35948ba5" Content-Length: 0 Both networks are connected via router without NAT. I can ping phones. Any idea why it does not work? The extension configuration was simple copied from old TB and only IP of server has been changed in phone configuration. How to debug it? what does mean "SIP/2.0 401 Unauthorized" - how to check what is wrong - pass or username?