secondary dns

Hello All

i want to make new DNS for my network i have 1Mbps with live IP but i got new DSL 20Mbps now i want to make new DNS with 20Mbps but i don`t want to use DSL line with firewall kindly Help me and what if i don`t use Firewall?

Thanks

here is the image

http://img15.imageshack.us/img15/2562/presentation1qf.jpg