[CentOS] Firewall frustration

> I spent much of the past 24 hours trying to find out how to set up 
> iptables for firewall routing WITHOUT NATing. Could not find anything.
> 

Eh? You just need to enable ip forwarding to enable routing. After that, 
it is put up the firewall rules as is necessary, build the appropriate 
routing tables on the firewall box and the boxes on the intranet(s).

iptables does not handle routing.