Proxy & Firewall Implementation

[John <naverxp () yahoo com sg>]

Hi

I'm a fresh graduate in System Administrator field. Recently, with much 
of luck, i was recommended to a company to implement a firewall system 
to their network infrastructure. I hope to pick some experience from 
this forum as to how people in here might consider different 
circumstances when placing their proxy server inside a protected network 
(behind the firwall) or before the firewall. Would i need two firewalls? 
(i'm considering the Cisco FW, and CyberGuard FW).

During my research, i found a documentation written by a blackhat whom 
suggested to allocate DMZ most of my services (httpd, mail, etc) outside 
the internal network and make redundancies everynight. My 2nd question, 
why did he suggested that? why expose my services outside the network 
where my information are Live and exposed to the risk of being compromised.

John