ZyXEL Communications Prestige 100, Руководство пользователя

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44 Configuring for Internet Access
Single User Account
Typically, if there are multiple users on the LAN wanting to
concurrently access the Internet, they will have to subscribe to
multiple IP addresses or a Class C subnetwork from the ISP. In
either case, these two approaches will cost more than a single user
account.
The Single User Account (SUA) feature allows customers to have
the same benefits as having a Class C address, but still only pay for
one IP address, thus saving significantly on subscription fees.
(Check with your ISP before you enable this feature).
This feature may also be used to connect to TCP/IP remote nodes
other than Internet Service Providers. For example this feature can
be used to simplify the allocation of IP addresses when connecting
branch offices to the corporate network.
The IP address for the Single User Account can be either fixed or
dynamically assigned by the ISP (or other remote node). In
addition, you can also configure a server, e.g., a Web server, on
your local network and make it accessible by outside users.
If you do not set a server IP address, SUA offers the additional
benefit of firewall protection. This is because if no server is
defined, all incoming inquiries will be filtered out by the Prestige
even if you do have a server on your network. This can prevent
intruders from probing your system.
The 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).
In summary: