Firewall configuration

["Nyandwi Patrick" <98043 anu ac ke>]

First of all, i have the DHCP server running.
Now the thing that i want is to bring in a Firewall which will be 
preventing some segments to access the WWW. 
What i want to know is if i can make the Server into a Firewall !!
But the problem of the setup comes in (Geographical !).

Do i have to get another comp and set it up as a Firewall then, from 
here i'll be restricting the users? 
Please send me some info if you have an idea, and some configuration 
steps !

Regards,
Pat