When Being a natural Internet firewall (NAT + Advanced Firewall), BILLION BROADBAND ROUTER protects your network from being accessed by outside users. There is only one IP address visible to outside users who are not able to access the specific server in your LAN. When you need to allow outside users to access local servers, e.g. Web server, FTP server, E-mail server or News server. You can set up a local server with specific port number that stands for the service, e.g. Web (80), FTP (21), Telnet (23), SMTP (25), POP3 (110), DNS (53), ECHO (7), NNTP (119) in section 3.4.6 ‘Virtual Server’ in user manual. When an incoming access request to the router for specified port is received, it will be forwarded to the corresponding internal server.
For example, if you set the Service Port number 80 (Web) to be mapped to the IP Address 192.168.1.2, then all incoming requests with router’s public IP address from outside users will be forwarded to the local server with IP address of 192.168.1.2.