ZyXEL Communications MAX-200M1 Series, Руководство пользователя

Страница: 98 / 258

ZyXEL MAX-200M1 Series User’s Guide
98 Chapter 9 NAT
Figure 53 Multiple Servers Behind NAT Example
9.1.2 Trigger Port Forwarding
Some services use a dedicated range of ports on the client side and a dedicated range of ports
on the server side. With regular port forwarding you set a forwarding port in NAT to forward a
service (coming in from the server on the WAN) to the IP address of a computer on the client
side (LAN). The problem is that port forwarding only forwards a service to a single LAN IP
address. In order to use the same service on a different LAN computer, you have to manually
replace the LAN computer's IP address in the forwarding port with another LAN computer's IP
address,
Trigger port forwarding solves this problem by allowing computers on the LAN to
dynamically take turns using the service. The ZyXEL Device records the IP address of a LAN
computer that sends traffic to the WAN to request a service with a specific port number and
protocol (a "trigger" port). When the ZyXEL Device's WAN port receives a response with a
specific port number and protocol ("incoming" port), the ZyXEL Device forwards the traffic
to the LAN IP address of the computer that sent the request. After that computer’s connection
for that service closes, another computer on the LAN can use the service in the same manner.
This way you do not need to configure a new IP address each time you want a different LAN
computer to use the application.
9.1.2.1 Trigger Port Forwarding Example
The following is an example of trigger port forwarding. In this example, J is Jane’s computer
and S is the Real Audio server.
Figure 54 Trigger Port Forwarding Process: Example