SMC Networks SMC7004ABR V.2 - Manual (Page 60)

Advanced Setup
57
Virtual Server
If you configure the Barricade™ Router as a virtual server,
remote users accessing services such as Web or FTP at your
local site via public IP addresses can be automatically redirected
to local servers configured with private IP addresses. In other
words, depending on the requested service (TCP/UDP port
number), the Barricade™ Router redirects the external service
request to the appropriate server (located at another internal IP
address).
For example, if you set Type/Public Port to TCP/80 (HTTP or
Web) and the Private IP/Port to 192.168.2.2/80, then all HTTP
requests from outside users will be transferred to 192.168.2.2 on
port 80. Therefore, by just entering the IP Address provided by
the ISP, Internet users can access the service they need at the
local address to which you redirect them.
The more common TCP service ports include:
HTTP: 80, FTP: 21, Telnet: 23, and POP3: 110.