ZyXEL Communications 480 - Manual (Page 56)

Prestige 480 ISDN Router
3-10 Internet Access
The IP address for the SUA can be either fixed or dynamically assigned when a call is connected.
In addition, you can designate servers using Menu 15, e.g., a web server and a telnet server, on
your local network and make them accessible to the outside world. For more information on setting
up servers see the section Multiple Servers behind SUA in the chapter Dial-in Server
Configuration.
If you do not define any server, SUA offers the additional benefit of firewall protection. If no
server is defined, all incoming inquiries will be filtered out by your Prestige and thus preventing
intruders from probing your network.
Your Prestige accomplishes this address sharing by translating the internal LAN IP addresses to a
single address that is globally unique on the Internet. For more information on IP address
translation, refer to RFC 1631, The IP Network Address Translator (NAT).
3.6.1 Advantages of SUA
In summary:
l SUA is a cost-effective solution for small offices with less than 64 hosts to access the Internet
or other remote TCP/IP networks.
l SUA supports servers to be accessible to the outside world.
l SUA can provide firewall protection if you do not specify a server. All incoming inquiries
will be filtered out by your Prestige.
l UDP and TCP packets can be routed. In addition, partial ICMP, including echo and trace
route, is supported.