User Manual

Chapter 10 NAT
LTE3301 Series User’s Guide
95
Fig ure 61 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 LTE3301 to record Jane’s computer IP address. The LTE3301
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 LTE3301 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 LTE3301
times out in three minutes with UDP (User Datagram Protocol), or two hours with TCP/IP (Transfer Control
Protocol/Internet Protocol).
10.6.5 Two Po ints To Re me m b e r Abo ut Trig g e r Po rts
1 Trigger events only happen on data that is coming from inside the LTE3301 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.
Jane’s com put e r
Real Au dio Se r v e r
Por t 7 0 7 0