Trigger Port Forwarding - ZyXEL Communications ZyWall 10W User Manual

LABEL
Global End IP
Apply
Reset
9.6

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 ZyWALL 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 ZyWALL's WAN port
receives a response with a specific port number and protocol ("incoming" port), the ZyWALL 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.
9.6.1 Trigger Port Forwarding Example
The following is an example of trigger port forwarding.
NAT Screens
Table 9-7 Address Mapping Edit
This is the ending Inside Global IP Address (IGA). This field is N/A for One-to-One,
Many-to-One and Server mapping types.
Click Apply to save your changes back to the ZyWALL.
Click Reset to begin configuring this screen afresh.
ZyWALL Series Internet Security Gateway
DESCRIPTION
9-13