I dont think your Mail and Proxy servers need two NIC cards. Essentially, the only thing needed in the scenario you described is to make sure that the LAN default gateway (the router connected to the LAN and the DMZ) is forwarding the IP ports that the proxy server is using, and the ports that Exchange is using.
The exact ports numbers you have to make sure go through will depend on the software setup, I know that a lot of proxy servers will use 1080 TCP, and depending on how the clients access Exchange youll have to configure the LAN gateway to pass things like Kerberos, NetBIOS, the Location Store, etc. Youll have to check with the software venders to see what ports they use.
Since the LAN gateway router is directly connected to the DMZ, you shouldnt need a static route you need to make sure that the firewall forwards the traffic addressed to the proxy and mail server that comes from the LAN.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.