Hi all,\n\nI have a problem with firewall (I think). I use DrayTek Vigor IPPBX 2820 as SIP server and to the outside I cal through ISDN. As SIP phone I use 3CX. In the internal network everything goes like charm. From outside network the phone registers perfect, but when I make a call (for exemple) to my mobile phone The rings, but when I answer it, the 3CX is do not recive answering message.