Hi, You should have those lines in you ser.cfg file. It means if someone is sending you a REGISTER message, instead of sending back an OK, SER sends back a challenge with 401 Unauthorized. Your sipphone is supposed to response with another REGISTER containing your password encrypted. Then SER responses with OK. if (method=="REGISTER") { if (!www_authorize("your.domain.com", "subscriber")) { www_challenge("your.domain.com ", "0"); return; }; save("location"); return; }; It's not a all a NAT or Firewall issue! Your client seams to be the problem! Regards, Paul -----Message d'origine----- De : serusers-bounces(a)iptel.org [mailto:serusers-bounces@lists.iptel.org] De la part de Joao Pereira Envoyé : samedi 29 avril 2006 18:08 À : serusers(a)lists.iptel.org Objet : [Serusers] 401 Unauthorized Hello to all Im trying to register SIP clients (Cisco IP phone and Planet VIP )that are located behind an ADSL line ( and behind NAT), and the first time they register, they receive the OK from SER, but when I reboot the phone, they cant connect again. They receive "401 Unauthorized" from SER. SER isnt returning "401 Unauthorized" in any part of ser.cfg Im not using firewall. Can the problem be in the type of NAT? Can someone help me? Thanks Joao Pereira _______________________________________________ Serusers mailing list serusers(a)lists.iptel.org http://lists.iptel.org/mailman/listinfo/serusers