ZyXEL Communications WAH7601 - Trigger Port Forwarding Example; Two Points to Remember about Trigger Ports

Chapter 10 NAT
WAH7601 User’s Guide
68
10.5.4 Trigger Port Forwarding Example
The following is an example of trigger port forwarding.
Figure 47 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 WAH7601 to record Jane’s computer IP address. The
WAH7601 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 WAH7601 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
WAH7601 times out in three minutes with UDP (User Datagram Protocol), or two hours with TCP/IP
(Transfer Control Protocol/Internet Protocol).
10.5.5 Two Points To Remember About Trigger Ports
1 Trigger events only happen on data that is coming from inside the WAH7601 and going to the outside.
2 If an application needs a continuous data stream, that port (range) will be tied up so that another
computer on the LAN cannot trigger it.