MitraStar Movistar GPT-2541GNAC, User Manual

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Chapter 6 Network Address Translation (NAT) 66
Trigger port forwarding solves this problem by allowing computers on the LAN to dynamically take
turns using the service. The Router 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
Router's WAN port receives a response with a specific port number and protocol ("open" port), the
Router 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.
For example:
Figure 36 Trigger Port Forwarding Process: Example
1 Jane requests a file from the Real Audio server (port 7070).
2 Port 7070 is a “trigger” port and causes the Router to record Jane’s computer IP address. The Router
associates Jane's computer IP address with the "open" port range of 6970-7170.
3 The Real Audio server responds using a port number ranging between 6970-7170.
4 The Router forwards the traffic to Jane’s computer IP address.
5 Only Jane can connect to the Real Audio server until the connection is closed or times out. The
Router times out in three minutes with UDP (User Datagram Protocol) or two hours with TCP/IP
(Transfer Control Protocol/Internet Protocol).
Click Advanced Setup > NAT > Port Triggering to manage your Router’s trigger port settings.
Figure 37 Port Triggering