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136 Chapter 8 Network Address Translation (NAT) Screens
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Figure 39 Trigger Port Forwarding process: example
1 Jane (A) requests a file from the Real Audio server (port 7070).
2 Port 7070 is a trigger port and causes the BCM50a Integrated Router to record
Jane’s computer IP address. The BCM50a Integrated Router associates Jane's
computer IP address with the incoming port range of 6970-7170.
3 The Real Audio server responds using a port number ranging between
6970-7170.
4 The BCM50a Integrated 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 BCM50a Integrated Router times out in three minutes with
UDP (User Datagram Protocol) or two hours with TCP/IP (Transfer Control
Protocol/Internet Protocol).
Two points to remember about Trigger Ports
Trigger events only happen on data that is coming from inside the BCM50a
Integrated Router and going to the outside.
If an application needs a continuous data stream, that port (range) is tied up so that
another computer on the LAN cannot trigger it.
BCM50a Integrated Router