I use SPA3102 with a iptel.org VoIP a/c, whenever my Firewall external IP changed (SPA3102's WAN port only connected to the internal LAN with a static IP, router function not used) the iptel.org VoIP a/c will report registration failed. I have to remove the proxy domain field and re-insert it then reboot to fix the problem, just wonder if this is a problem on the SER side or on the SPA side.  I am sorry if this is not a correct appropriate place to ask such a question.