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NB6, NB6W, NB6Plus4, NB6Plus4W, NB6Plus4Wn User Guide YML854Rev1
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Virtual Server – Port Forwarding
The Router implements NAT to make your entire local network appear as a single machine to the Internet.
The typical situation is that you have local servers for different services and you want to make them publicly
accessible. With NAT applied, it will translate the internal IP addresses of these servers to a single IP address
that is unique on the Internet. NAT function not only eliminates the need for multiple public IP addresses but
also provides a measure of security for your LAN.
When the router receives an incoming IP packet requesting for accessing your local server, the router will
recognize the service type according to the port number in this packet (e.g., port 80 indicates HTTP service
and port 21 indicates FTP service). By specifying the port number, the router knows which service should be
forwarded to the local IP address that you specified.
After setting the virtual server, you should modify the filter rule about the port and service information which
you set on the virtual server. Because the firewall protects the router by filter rule, you should update the filter
rule after you set up the virtual server.
Virtual Server function allows you to make servers on your LAN accessible to Internet users. Normally, Internet
users would not be able to access a server on your LAN because:
• Your server does not have a valid external IP Address.
• Attempts to connect to devices on your LAN are blocked by the firewall in this device.
The Virtual Server feature solves these problems and allows Internet users to connect to your servers, as
illustrated below:
Internet
Router
203.70.212.52
(WAN IP Address)
192.196.1.1
(LAN IP Address)
192.196.1.0
(Web Server)
192.196.1.20
(FTP Server)
http://203.70.212.52
(Remote PC using Web Server)
ftp://203.70.212.52
(Remote PC using FTP Server)