Hello ,

I get after the REGISTER a 501. What can be the problem ? 

tested with Fritzbox and also CISCO SPA ATA

Trace

--
17:34:29.088 0 L 12 00010000-[SOIO -SO1 ] SIPR (615 byte) Remote 192.168.110.1:5060/UDP Local 192.168.110.250:9803/UDP
17:34:29.088 0 L 12 00010000-[SIP -IOL1 ] SIPR (615 byte) Remote 192.168.110.1:5060/UDP Local 192.168.110.250:9803/UDP
17:34:29.088 0 L 12 00010000- >REGISTER sip:192.168.110.250 SIP/2.0
17:34:29.088 0 L 12 00010000- >Via: SIP/2.0/UDP 192.168.110.1:5060;rport;branch=z9hG4bK83A6B88BD04D56F3
17:34:29.088 0 L 12 00010000- >Route: <sip:192.168.110.250:9803;lr>
17:34:29.088 0 L 12 00010000- >From: <sip:29@192.168.110.250>;tag=1388388833
17:34:29.088 0 L 12 00010000- >To: <sip:29@192.168.110.250>
17:34:29.088 0 L 12 00010000- >Call-ID: 0292D8A76FDF33B6@192.168.110.1
17:34:29.088 0 L 12 00010000- >CSeq: 11 REGISTER
17:34:29.088 0 L 12 00010000- >Max-Forwards: 70
17:34:29.088 0 L 12 00010000- >User-Agent: AVM FRITZ!Box 7490 113.06.30 (Jul 10 2015)
17:34:29.088 0 L 12 00010000- >Supported: 100rel,replaces
17:34:29.088 0 L 12 00010000- >Allow-Events: telephone-event,refer,reg
17:34:29.088 0 L 12 00010000- >Allow: INVITE,ACK,OPTIONS,CANCEL,BYE,UPDATE,PRACK,INFO,SUBSCRIBE,NOTIFY,REFER,MESSAGE,PUBLISH
17:34:29.088 0 L 12 00010000- >Accept: application/sdp, multipart/mixed
17:34:29.088 0 L 12 00010000- >Accept-Encoding: identity
17:34:29.088 0 L 12 00010000- >Content-Length: 0
17:34:29.088 0 L 12 00010000- >
17:34:29.089 0 L 12 00010000-[SIP -TXN173 ] sipopenchannel save Listen IP:0.0.0.0 Rport:0 Remote IP:192.168.110.1 Rport:5060 Local IP:0.0.0.0 Lport:0 Proto:UDP
17:34:29.090 1 L 12 00010000-[SIP -TXN173 ] SIPX (370 byte) Remote 192.168.110.1:5060/UDP Local 192.168.110.250:9803/UDP
17:34:29.090 1 L 12 00010000- >SIP/2.0 501 Not Implemented
17:34:29.090 1 L 12 00010000- >Via: SIP/2.0/UDP 192.168.110.1:5060;received=192.168.110.1;rport=5060;branch=z9hG4bK83A6B88BD04D56F3
17:34:29.090 1 L 12 00010000- >From: <sip:29@192.168.110.250>;tag=1388388833
17:34:29.090 1 L 12 00010000- >To: <sip:29@192.168.110.250>;tag=sipcontrol_545917648-51776368
17:34:29.090 1 L 12 00010000- >Call-ID: 0292D8A76FDF33B6@192.168.110.1
17:34:29.090 1 L 12 00010000- >CSeq: 11 REGISTER
17:34:29.090 1 L 12 00010000- >Contact: <sip:anonymous@192.168.110.250:9803>
17:34:29.090 1 L 12 00010000- >Content-Length: 0
17:34:29.090 1 L 12 00010000- >
17:34:29.090 1 L 12 00010000-[SOIO -SO1 ] SIPX (370 byte) Remote 192.168.110.1:5060/UDP Local 192.168.110.250:9803/UDP
17:34:29.094 1 L 12 00010000-[SOIO -SO1 ] SIPR (698 byte) Remote 192.168.110.1:5060/UDP Local 192.168.110.250:9803/UDP
17:34:29.094 1 L 12 00010000-[SIP -IOL1 ] SIPR (698 byte) Remote 192.168.110.1:5060/UDP Local 192.168.110.250:9803/UDP
17:34:29.094 1 L 12 00010000- >REGISTER sip:192.168.110.250 SIP/2.0
17:34:29.094 1 L 12 00010000- >Via: SIP/2.0/UDP 192.168.110.1:5060;rport;branch=z9hG4bK27FC0520A37D7A9A
17:34:29.094 1 L 12 00010000- >Route: <sip:192.168.110.250:9803;lr>
17:34:29.094 1 L 12 00010000- >From: <sip:29@192.168.110.250>;tag=1388388833
17:34:29.094 1 L 12 00010000- >To: <sip:29@192.168.110.250>
17:34:29.094 1 L 12 00010000- >Call-ID: 0292D8A76FDF33B6@192.168.110.1
17:34:29.094 1 L 12 00010000- >CSeq: 12 REGISTER
17:34:29.094 1 L 12 00010000- >Contact: <sip:29@192.168.110.1;uniq=2EA31847AF0150DE8A60E37E6D221>
17:34:29.094 1 L 12 00010000- >Max-Forwards: 70
17:34:29.094 1 L 12 00010000- >Expires: 1800
17:34:29.094 1 L 12 00010000- >User-Agent: AVM FRITZ!Box 7490 113.06.30 (Jul 10 2015)
17:34:29.094 1 L 12 00010000- >Supported: 100rel,replaces
17:34:29.094 1 L 12 00010000- >Allow-Events: telephone-event,refer,reg
17:34:29.094 1 L 12 00010000- >Allow: INVITE,ACK,OPTIONS,CANCEL,BYE,UPDATE,PRACK,INFO,SUBSCRIBE,NOTIFY,REFER,MESSAGE,PUBLISH
17:34:29.094 1 L 12 00010000- >Accept: application/sdp, multipart/mixed
17:34:29.094 1 L 12 00010000- >Accept-Encoding: identity
17:34:29.094 1 L 12 00010000- >Content-Length: 0
17:34:29.094 1 L 12 00010000- >
17:34:29.095 1 L 12 00010000-[SIP -TXN175 ] sipopenchannel save Listen IP:0.0.0.0 Rport:0 Remote IP:192.168.110.1 Rport:5060 Local IP:0.0.0.0 Lport:0 Proto:UDP
17:34:29.095 1 L 12 00010000-[SIP -TXN175 ] SIPX (370 byte) Remote 192.168.110.1:5060/UDP Local 192.168.110.250:9803/UDP
17:34:29.095 1 L 12 00010000- >SIP/2.0 501 Not Implemented
17:34:29.095 1 L 12 00010000- >Via: SIP/2.0/UDP 192.168.110.1:5060;received=192.168.110.1;rport=5060;branch=z9hG4bK27FC0520A37D7A9A
17:34:29.095 1 L 12 00010000- >From: <sip:29@192.168.110.250>;tag=1388388833
17:34:29.095 1 L 12 00010000- >To: <sip:29@192.168.110.250>;tag=sipcontrol_545922648-51972976
17:34:29.095 1 L 12 00010000- >Call-ID: 0292D8A76FDF33B6@192.168.110.1
17:34:29.095 1 L 12 00010000- >CSeq: 12 REGISTER
17:34:29.095 1 L 12 00010000- >Contact: <sip:anonymous@192.168.110.250:9803>
17:34:29.095 1 L 12 00010000- >Content-Length: 0
17:34:29.095 1 L 12 00010000- >
17:34:29.095 1 L 12 00010000-[SOIO -SO1 ] SIPX (370 byte) Remote 192.168.110.1:5060/UDP Local 192.168.110.250:9803/UDP