ZyXEL Communications 802.11g Wireless Firewall Router P-320W - Manual (Page 106)

P-320W User’s Guide
106 Chapter 8 Network Address Translation (NAT)
The following table describes the labels in this screen.
Table 44 NAT: Port Forwarding: Rule Setup
LABEL DESCRIPTION
Active Select the check box to enable this port forwarding entry.
Clear the checkbox to disallow forwarding of these ports to an inside server without
having to delete the entry.
Service Name Type a Service Name to identify this port-forwarding rule.
Start Port Type a start port number. To forward only one port, enter it again in the End Port
field. To specify a range of ports, enter the last port to be forwarded in the End
Port field.
End Port Type an end port number.
Server IP Address Type the inside IP address of the server.
Apply Click Apply to save your changes back to the Prestige.
Cancel Click Cancel to return to the previous screen and not save your changes.
8.4 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 Prestige 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 Prestige's WAN port receives a response with a specific
port number and protocol ("incoming" port), the Prestige 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.
8.4.1 Trigger Port Forwarding Example
The following is an example of trigger port forwarding.