ZyXEL Communications NR2101 - Two Points to Remember about Trigger Ports

Chapter 8 NAT
NR2101 User’s Guide
80
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 NR2101 to record Jane’s computer IP address. The NR2101
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 NR2101 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 NR2101
times out in three minutes with UDP (User Datagram Protocol), or two hours with TCP/IP (Transfer Control
Protocol/Internet Protocol).
8.3.5 Two Points To Remember About Trigger Ports
1 Trigger events only happen on data that is coming from inside the NR2101 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.