Technical Reference; Nat Port Forwarding: Services And Port Numbers; Nat Port Forwarding Example - ZyXEL Communications NBG-418N v2 User Manual

Table 45 Network > NAT > Port Triggering (continued)
LABEL
Start Related
Port
End Related
Port
Open Protocol
Apply
Cancel

10.6 Technical Reference

The following section contains additional technical information about the NBG-418N v2 features
described in this chapter.

10.6.1 NAT Port Forwarding: Services and Port Numbers

A port forwarding 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 Application screen 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.

10.6.2 NAT Port Forwarding Example

Let's say you want to assign ports 21-25 to one FTP, Telnet and SMTP server (A in the example),
port 80 to another (B in the example) and assign a default server IP address of 192.168.1.35 to a
third (C in the example). You assign the LAN IP addresses and the ISP assigns the WAN IP address.
The NAT network appears as a single host on the Internet.
Chapter 10 Network Address Translation
DESCRIPTION
Type a Starting port number that is related to the open protocol.
Type a Ending port number that is related to the open protocol.
The open protocol is the protocol (UDP, TCP or UDP/TCP) that causes (or triggers) the
NBG-418N v2 to record the IP address of the LAN computer that sent the traffic to a
server on the WAN.
Click Apply to save your changes back to the NBG-418N v2.
Click Cancel to begin configuring this screen afresh.
NBG-418N v2 User's Guide
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