ZyXEL Communications NBG-419N Router, Figure 102 Trigger Port Forwarding Process: Example, The following is an example of trigger port forwarding

Chapter 16 Network Address Translation (NAT)

16.5.1 Trigger Port Forwarding Example

The following is an example of trigger port forwarding.Figure 102 Trigger Port Forwarding Process: ExampleRouter

Router

1Jane requests a file from the Real Audio server (port 7070).

2Port 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 "incoming" port range of 6970-7170.

3The Real Audio server responds using a port number ranging between 6970-7170.4The Router forwards the traffic to Jane’s computer IP address.

5Only 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).

16.5.2Two Points To Remember About Trigger Ports

1Trigger events only happen on data that is going coming from inside the Router and going to the outside.

If an application needs a continuous data stream, that port (range) will be tied up so that another computer on the LAN can’t trigger it.

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	NBG-419N v2 User’s Guide