ZyXEL Communications NBG-318S - Manual (Page 121)

Chapter 10 Network Address Translation (NAT)
NBG-318S User’s Guide
121
Figure 67 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 NBG-318S to record Jane’s computer IP
address. The NBG-318S 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 NBG-318S 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 NBG-318S times out in three minutes with UDP (User Datagram Protocol), or
two hours with TCP/IP (Transfer Control Protocol/Internet Protocol).
10.5.2 Two Points To Remember About Trigger Ports
1 Trigger events only happen on data that is going coming from inside the NBG-318S 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 can’t trigger it.
10.6 NAT Advanced Screen
To change your NBG-318S’s trigger port settings, click Network > NAT > Advanced. The
screen appears as shown.
"
Only one LAN computer can use a trigger port (range) at a time.