ZyXEL Communications Prestige 480 - Manual (Page 79)

Prestige 480 Dual BRI ISDN Router
Internet Access 3-15
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. Fo r more information on IP address translation, refer to RFC
1631, The IP Network Address Translator (NAT) .
3.7.1 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.