ZyXEL p-2302hw-p1 Manual Do Utilizador

P-2302HW/HWL-P1 Series User’s Guide

Chapter 8 NAT

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1 Jane requests a file from the Real Audio server (port 7070).

2 Port 7070 is a “trigger” port and causes the ZyXEL Device to record Jane’s computer IP 

address. The ZyXEL Device 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 ZyXEL Device 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 ZyXEL Device times out in three minutes with UDP (User Datagram Protocol), 
or two hours with TCP/IP (Transfer Control Protocol/Internet Protocol). 

1 Trigger events only happen on data that is coming from inside the ZyXEL Device 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. 

Some NAT routers may include a SIP Application Layer Gateway (ALG). A SIP ALG allows 
SIP calls to pass through NAT by examining and translating IP addresses embedded in the data 
stream. When the ZyXEL Device registers with the SIP register server, the SIP ALG translates 
the ZyXEL Device’s private IP address inside the SIP data stream to a public IP address. You 
do not need to use STUN or an outbound proxy (see 

) if your ZyXEL 

Device is behind a SIP ALG.

Use this screen to enable and disable NAT and to allocate memory for NAT and firewall rules. 
To access this screen, click Network > NAT > General.