Chapter 10 Network Address Translation (NAT)
The following table describes the labels in this screen.
Table 56 NAT General
LABEL | DESCRIPTION |
Active Network | Select this check box to enable NAT. |
Address |
|
Translation (NAT) |
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|
SUA Only | Select this radio button if you have just one public WAN IP address for your |
| ZyXEL Device. |
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|
Full Feature | Select this radio button if you have multiple public WAN IP addresses for your |
| ZyXEL Device. |
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|
Max NAT/Firewall | When computers use peer to peer applications, such as file sharing applications, |
Session Per User | they need to establish NAT sessions. If you do not limit the number of NAT |
| sessions a single client can establish, this can result in all of the available NAT |
| sessions being used. In this case, no additional NAT sessions can be |
| established, and users may not be able to access the Internet. |
| Each NAT session establishes a corresponding firewall session. Use this field to |
| limit the number of NAT/firewall sessions each client computer can establish |
| through the ZyXEL Device. |
| If your network has a small number of clients using peer to peer applications, you |
| can raise this number to ensure that their performance is not degraded by the |
| number of NAT sessions they can establish. If your network has a large number |
| of users using peer to peer applications, you can lower this number to ensure no |
| single client is using all of the available NAT sessions. |
|
|
Enable SIP ALG | Select this to make sure SIP (VoIP) works correctly with |
| |
| 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 if your ZyXEL Device is behind a SIP ALG. |
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Apply | Click Apply to save your changes to the ZyXEL Device. |
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Cancel | Click Cancel to reload the previous configuration for this screen. |
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10.4 Port Forwarding
A port forwarding set is a list of inside (behind NAT on the LAN) servers, for example, web or FTP, that you can make visible to the outside world even though NAT makes your whole inside network appear as a single computer to the outside world.
You may enter a single port number or a range of port numbers to be forwarded, and the local IP address of the desired server. The port number identifies a service; for example, web service is on port 80 and FTP on port 21. In some cases, such as for unknown services or where one server can support more than one service (for example both FTP and web service), it might be better to specify a range of port numbers. You can allocate a server IP address that corresponds to a port or a range of ports.
Many residential broadband ISP accounts do not allow you to run any server processes (such as a Web or FTP server) from your location. Your ISP may periodically check for servers and may suspend your account if it discovers any active services at your location. If you are unsure, refer to your ISP.
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