うちはこんな感じ。(正常に使えてるときのログの抜粋だけど)

VoIP SIP:DNS Request OK hostname=ipphone.plala.or.jp
VoIP SIP:RegisterDNSResult result=0,address=-634872262
VoIP SIP SND: REGISTER sip:ipphone.plala.or.jp SIP/2.0
VoIP SIP RCV: SIP/2.0 401 Unauthorized
VoIP SIP SND: REGISTER sip:ipphone.plala.or.jp SIP/2.0
VoIP SIP RCV: SIP/2.0 200 OK
VoIP SIP SND: REGISTER sip:ipphone.plala.or.jp SIP/2.0
VoIP SIP RCV: SIP/2.0 401 Unauthorized
VoIP SIP SND: REGISTER sip:ipphone.plala.or.jp SIP/2.0
VoIP SIP RCV: SIP/2.0 200 OK