The Port Triggering Screen - ZyXEL Communications VMG8825-B Series User Manual

Figure 87 Applications: Add
The following table describes the labels in this screen.
Table 60 Applications: Add
LABEL
WAN Interface
Server IP
Address
Application
Category
Application
Forwarded
View Rule
OK
Cancel

11.4 The Port Triggering Screen

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 VMG 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 VMG's WAN port
receives a response with a specific port number and protocol ("open" port), the VMG 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.
Chapter 11 Network Address Translation (NAT)
DESCRIPTION
Select the WAN interface that you want to apply this NAT rule to.
Enter the inside IP address of the application here.
Select the category of the application from the drop-down list box.
Select a service from the drop-down list box and the VMG automatically configures the
protocol, start, end, and map port number that define the service.
Click this to display the configuration of the service that you have chosen in Application
Fowarded.
Click OK to save your changes.
Click Cancel to exit this screen without saving.
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