Nortel BayStack 820 Installation And Reference Manual page 139

Configuring Advanced Router Options
NAT extends the concept of private addressing to provide a way to specify which
applications on the LAN you want Internet users to be able to access. To do this,
you configure the router to reroute an Internet packet it receives from the Internet
to the TCP or UDP port that the application uses on the privately-addressed LAN
server that is running that application.
For example, a privately-addressed server on your LAN that is running a Web
application, can be accessed from the Internet by configuring the router to
translate all packets addressed to its public address containing the destination port
80 (the standard HTTP port), to a privately-addressed server that is running a Web
server application. Remote Internet users do not know about, nor can they access,
any other services or applications running on the server with which they are
communicating. In this manner a server application is "mapped" to a port on the
router.
When you map port 80 (HTTP) or port 23 (Telnet) to a private IP address,
special consideration must given for remote administration of the BayStack 820
ISDN Router because those ports are normally used for the Web-based BayStack
820 ISDN Router Manager software (port 80) and the command line interface
(port 23).
If you remap port 80, you must remap port 80 on the router to another port and
then access the BayStack 820 ISDN Router Manager software using the remapped
port. Similarly, if you remap port 23, you must re-map port 23 on the router to
another port and access the command line interface using the remapped port.
LAN-based administration remains unchanged.
Note: If the BayStack 820 ISDN Router Manager software is remapped to
port 8080, you must use the extended URL format to access the router, for
example, http://192.168.168.230:8080.
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