The X-lite client is installed behind an ADSL router and it seems the ISP also has a firewall supposedly protecting their ADSL customers blocking some netbios ports and non-critical. I can't make outbound calls but I can receive but before then I had to use the following in the account section in SIP.conf [2222] ... type=friend secret=xxxx host=dynamic ;dtmfmode=inband ; Choices are inband, rfc2833, or info nat=yes callerid = "xxxxxx" <(216) 22222222> defaultip=x.x.x.x I keep getting this error when I enable SIP Debug. Transmitting (NAT): SIP/2.0 401 Unauthorized Does have an idea what is going on?