This description was taken from the User's Guide, see at www.bintec.de
How do I configure Internet access for my LAN using NAT?
Using NAT, or Network Address Translation, the BRICK can connect
your LAN to the Internet using a single IP address. This IP address can be
a static address or dynamically assigned by your Internet Service Provid-er
(ISP) at connection time. The beauty of using NAT is that you don’t
need an official IP address for every host on the LAN and NAT provides
you a built-in firewall that protects your LAN from intruders.
You’ll need the following information provided by your ISP.
&127 Your ISP’s ISDN telephone number.
&127 The PPP ID of the system your BRICK will dial into.
&127 The BRICK’s PPP Password.
&127 An IP address (not
needed if assigned dynamically).
Configure a new ISDN interface for your ISP. Here you’ll need to set:
Partner Name <ISP Name>
Encapsulation PPP
Identify by Calling Number <yes or no>
PPP Authentication Protocol PAP and CHAP
Partner PPP ID <PPP ID of ISP’s system>
PPP Password <PPP password assigned by ISP>
ISDN Number <your ISP’s ISDN telephone number>
Direction outgoing
If your address is assigned dynamically all you need to do here is set
IP Transit Network to "dynamic". Otherwise set the fields as follows:
IP Transit Network yes
Local ISDN IP Address <BRICK’s static IP Address>
Partner ISDN IP Address <BRICK’s static IP Address>
From this list, select the ISP interface you just configured.
Network Address Translation on
Now configure the types of incoming connections you want to allow.
Under 
specify the internal
host, and services to allow.
You might want to allow access to an FTP server on the LAN.
Service ftp
Destination <IP address of your FTP server>
All that’s left to do now is to add a default route to your ISP.
Route Type Default route
Network WAN without transit network
Partner / Interface <ISP interface name>
Additional Routing Settings: Note that routing settings on some work-stations
on your LAN may need to be modified to include a default route
that specifies the BRICK’s LAN address. Check your operating system’s
instructions to see what changes need to be made.
&127 On most UNIX workstations, you can add the route with:
route add default <BRICK’s LAN Address> 1
This may not be needed if the workstation understands RIP. It
will learn about new routes from the BRICK every 30 seconds.
&127 On Windows 95 systems with Microsoft TCP/IP change "Prop-erties–
Systemcontrol–Network–TCP/IP-Properties–Gateway"
and add the BRICK as the primary gateway.
Another option is to use Proxy ARP on the LAN. T ADVANCED SETTINGS
IP
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