Two Points To Remember About Trigger Ports - ZyXEL Communications NBG6515 User Manual

Trigger Port Forwarding Process: Example
Fig ure 87
Jane requests a file from the Real Audio server (port 7070).
1
Port 7070 is a "trigger" port and causes the NBG to record Jane's computer IP address. The NBG
2
associates Jane's computer IP address with the "incoming" port range of 6970-7170.
The Real Audio server responds using a port number ranging between 6970-7170.
3
The NBG forwards the traffic to Jane's computer IP address.
4
Only Jane can connect to the Real Audio server until the connection is closed or times out. The NBG
5
times out in three minutes with UDP (User Datagram Protocol), or two hours with TCP/IP (Transfer Control
Protocol/Internet Protocol).
16.5.2 T wo Po ints T o Re m e m b e r Ab o ut T rig g e r Po rts
Trigger events only happen on data that is going coming from inside the NBG and going to the outside.
1
If an application needs a continuous data stream, that port (range) will be tied up so that another
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computer on the LAN can't trigger it.
Chapter 16 Network Address Translation (NAT)
Router
NBG6515 User's Guide
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