ZyXEL NBG4615 User Manual download pdf (Page 177)

Chapter 20 NAT

NBG4615 User’s Guide

177

20.5 Technical Reference

The following section contains additional technical information about the NBG4615 features

described in this chapter.

20.5.1 NATPort 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.

20.5.2 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.

Figure 113 Multiple Servers Behind NAT Example

1 2 ... 172 173 174 175 176 177 178 179 180 181 182 ... 363 364

No comments

ZyXEL NBG4615 User Manual Page 177