It is beyond the scope of this presentation to describe how to configure a network interface. However, I will describe the reasons for some of the choices that will come up in making this setup work.
You must set up your private network properly. For this, I have chosen IP addresses that look like 192.168.1.1, 192.168.1.2, 192.168.1.3, etc. The following should explain why.
From IP Masquerade FAQ:
There is an RFC (#1597) on which IP addresses are to be used on a non-
connected network. There are 3 blocks of numbers set aside
specifically for this purpose. One which I use is 255 Class-C subnets
at 192.168.1.n to 192.168.255.n .
From RCF 1597:
Section 3: Private Address Space
The Internet Assigned Numbers Authority (IANA) has reserved the
following three blocks of the IP address space for private networks:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
We will refer to the first block as "24-bit block", the second as
"20-bit block", and to the third as "16-bit" block". Note that the
first block is nothing but a single class A network number, while the
second block is a set of 16 contiguous class B network numbers, and
third block is a set of 255 contiguous class C network numbers.
So, if you're using a class C network, you should name your machines
as 192.168.1.1, 1.92.168.1.2, 1.92.168.1.3, ..., 192.168.1.x
192.168.1.1 is usually the gateway machine, which is your Linux host
connecting to the Internet. Notice that 192.168.1.0 and 192.168.1.255
are the Network and Broadcast address respectively, which are
reserved. Avoid using these addresses on your machines.
Therefore, if you have already set up a network for your computers in one of the above ranges, all is well. However, if they are not, then you should probably change to one of the address blocks listed above.