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ZyWALL 50 Internet Security Gateway
NAT 6-13
6.4 NAT Server Sets – Port Forwarding
A NAT server set is a list of inside (behind NAT on the LAN) servers, for example, web or FTP, that you
can make visible to the outside world even though NAT makes your whole inside network appear as a
single machine to the outside world.
can make visible to the outside world even though NAT makes your whole inside network appear as a
single machine to the outside world.
Use Menu 15 - NAT Setup 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. Entry 12
(port 1026) is non-editable (see Figure 6-10).
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. Entry 12
(port 1026) is non-editable (see Figure 6-10).
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.
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.
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 included disk for more examples and details on
NAT.
information about port numbers. Please also refer to the included disk for more examples and details on
NAT.
Table 6-7 Services & Port Numbers
SERVICES PORT
NUMBER
ECHO
7
FTP (File Transfer Protocol)
21
Telnet
23
SMTP (Simple Mail Transfer Protocol)
25
DNS (Domain Name System)
53