IP Range and Routing for security

Hi peeps I currently have a quite simple network setup of a few internal subnets passing over a router on a stick (cisco 1721) with a Fedora 10 Linux box looking after the NAT and port forwarding for servers etc with 1 external IP.

This works fine but thankfully management gave the go ahead on a 10Mbit leased line. This goes lives in a couple of weeks and I am trying to suss the best way to handle securing and routing the new IP range (we are getting a /27 with the pipe). I'd like to use some of these IP's on our Windows servers to remove the limitations of port forwarding from the linux firewall.

My question is can I desgin the network in such a way that the linux box can firewall the /27 for the windows servers. I understand that it can be subnetted again to then use the linux firewall as the gateway, but my thinking (probably wrong) is that the ISP router will also need  routes to force the incoming taffic to pass through the linux box before heading to the desitnation IP on the windows server?

I was thinking of a software firewall solution but this seems unmanageable once a few of the machines get public IP's.

Any advice on the best way approach this would be appreciated.

Cheers

Paul
PaulCousins1Asked:
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DCMBSCommented:
I wouldn't do this.  I wouldn't give my servers a public ip unless there was an compelling reason to do so.  NAT is one of the best defences there is to protect your network.
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PaulCousins1Author Commented:
Unfortunately needs must and we do require some of the servers to have a public IP.

An alternative i consdiered would be a 2nd liunx box with muliplte NICS or virtual interfaces forwarding external IP's in but this seems a bit to prone to failure for obvious reasons.

SMTP Backup, DNS Server and IPSEC VPN are just the ones i can think off off the top of my head. It may only be 1 extra server with a public IP but as I said needs must i'm afraid.

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DCMBSCommented:
I think you would be better advised to install a hardware firewall such as a Zywall 5 or similar which can do 1 to 1 NAT to publish your servers.  I have set up many a network for small to medium business and I have never had to give an internal server a public IP.  The only real difficulty here is the IPSEC VPN whicch I am sure can be resolved without exposing your servers to the internet.  perhaps just one server for terminating the VPNs placed in the DMZ.  Or perhaps a dedicated VPN gateway.
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