ZyXEL Communications NBG-417N User Manual page 109

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.
Port forwarding allows you to define the local servers to which the incoming services will be
forwarded. To change your NBG-417N's port forwarding settings, click Network > NAT >
Application. The screen appears as shown.
Note: If you do not assign a Default Server IP address in the NAT > General screen,
the NBG-417N discards all packets received for ports that are not specified in this
screen or remote management.
Refer to Appendix E on page 235
Figure 72 Network > NAT > Application
NBG-417N User's Guide
Chapter 10 Network Address Translation (NAT)
for port numbers commonly used for particular services.
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