Linux Security Proxy S./ Firewall - Urgent help needed

[mmandua]

Hi everyone, when i meet people and tell me i choose the easiest work, to be i IT, it remind me all the nights a lose trying to get solutions for my organisation.

I have attached my scenario:
under the firewall i have DMZ Servers (Web Server, DMZ DNS, spam filter ...) the proxy its squid and runs under debian lenny, and for forwarding i have shorewall. I want enable some services from dmz to be accessed on my local network. like spam filter must contact the MS Exchange on lan, the insternal dns server that runs on windows must get response from bind on dmz.

Please help me on how to archive this. i have tryied to implement nat but doesn't seam to be the solution.

Any help on this will be apprecieted. you can just redirect me to a book or other links.

Best regards
Messias

[dmk06]

Here is a guide:
link: http://linuxman.wikispaces.com/Creat...mall+nonprofit


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And another guide:
link:
About My Network


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And here is a similar post:
link:
WebServer/DMZ/SQUID Secure Access