D-Link DFL-600 - Manual (Page 49)

Advanced Settings
NAT
Network Address Translation
Network Address Translation (NAT) is a routing protocol that allows your
network to become a private network that is isolated from, yet connected to
the Internet. It does this by changing the IP address of packets from a global
IP address
− assigned by your ISP − usable on the Internet to a local IP
address − assigned by you − usable on your private network (but not on the
Internet.)
Virtual Servers
Virtual Servers allow remote users to access services on your LAN such as
FTP for file transfers or SMTP and POP3 for e-mail. The DFL-600 will
accept remote requests for these services at a Global IP Address you specify,
using the specified TCP or UDP protocol and port number, and then redirect
these requests to the server on your LAN with the Private IP address you
specify.