How to connect three different network using redhat linux 9 - clients are window 2000

hello friends.

The present situation is,

we have one linux server, that server has two ethernet cards. one act
as gateway to connect internet, another card is sharing internet to
LAN.

Now i need to separate single LAN into two different networks. And i
have to share internet to these two networks.

if there is any possible to access within these two networks throu
redhat Linux 9. The clinet are windows 2000.

every hits are appreciated.

thank you

pvn