ZyXEL Communications G-2000 Plus V2, User Manual

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ZyXEL G-2000 Plus v2 User’s Guide
118 Chapter 8 Single User Account (SUA) / Network Address Translation (NAT)
Many residential broadband ISP accounts do not allow you to run any server processes (such
as a Web or FTP server) from your location. Your ISP may periodically check for servers and
may suspend your account if it discovers any active services at your location. If you are
unsure, refer to your ISP.
8.3.1 Default Server IP Address
In addition to the servers for specified services, NAT supports a default server IP address. A
default server receives packets from ports that are not specified in this screen
Note: If you do not assign a Default Server IP Address, the ZyXEL device discards all
packets received for ports that are not specified in this screen or remote
management.
8.3.2 Port Forwarding: Services and Port Numbers
A NAT server set is a list of inside (behind NAT on the LAN) servers, for example, web or
FTP, that you can make accessible to the outside world even though NAT makes your whole
inside network appear as a single machine to the outside world.
Use the SUA Server page to forward incoming service requests to the server(s) on your local
network. You may enter a single port number or a range of port numbers to be forwarded, and
the local IP address of the desired server. The port number identifies a service; for example,
web service is on port 80 and FTP on port 21. In some cases, such as for unknown services or
where one server can support more than one service (for example both FTP and web service),
it might be better to specify a range of port numbers.
In addition to the servers for specified services, NAT supports a default server. A service
request that does not have a server explicitly designated for it is forwarded to the default
server. If the default is not defined, the service request is simply discarded.
Note: Many residential broadband ISP accounts do not allow you to run any server
processes (such as a Web or FTP server) from your location. Your ISP may
periodically check for servers and may suspend your account if it discovers any
active services at your location. If you are unsure, refer to your ISP.
The most often used port numbers are shown in the following table. Please refer to RFC 1700
for further information about port numbers. Please also refer to the Supporting CD for more
examples and details on SUA/NAT.