ZyXEL Communications EMG6765-Q10A, Руководство пользователя

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Chapter 13 NAT
EMG6765-Q10A User’s Guide
118
Figure 65 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 EMG6765-Q10A to record Jane’s computer IP address. The
EMG6765-Q10A 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 EMG6765-Q10A 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
EMG6765-Q10A times out in three minutes with UDP (User Datagram Protocol), or two hours with TCP/IP
(Transfer Control Protocol/Internet Protocol).
13.5.5 Two Points To Remember About Trigger Ports
1
Trigger events only happen on data that is coming from inside the EMG6765-Q10A 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.