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Firewall with 1 Nic

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Firewall with 1 Nic - 4.Aug.2003 10:58:00 AM   


Posts: 2
Joined: 28.Jul.2003
Status: offline
Hi All

I have been experimenting with a lab ISA server and found some interesting things
which I hope you can assist with.

I wanted to see if I could get ISA sever to work as a firewall with 1 physical nic.
I came to the conclusion, after reading the message boards and Tom's articles
That ISA server can only function as a firewall with 2 nics 1 external, 1 internal.

So I installed 1 physical nic connected to the network,bound a IP and dubbed it internal in the LAT
I then installed a Dummy Software Adapter ( MS loopback adapter) and bound a external IP,
thus emulating an external interface.

It seemed to work as everything was blocked until I setup the relevant packet filter
to allow me to access to services on the 'internal' interface, which where Terminal services,

Here is the setup

1.) ISA server( SP1,FP1 and all patches) , Win2k Server (SP4)
2.) 1 Physical NIC, connected to the network (Internal), included in LAT
3.) 1 Software NIC, External IP.
4.) Packet Filtering

Although this is working now in the LAB, could this be pulled off in the production environment, without using a back to back setup.

Here is the real life scenorio I needed to emulate :

1.) Web server connected directly to the internet ( 1 Physical Nic), hosted at an ISP who don't provide Firewall services.
2.) No resources for a back to back config.

I would appreciate any help
Thanks in advance -P.S Thanks for the great site !
Post #: 1
RE: Firewall with 1 Nic - 4.Aug.2003 8:10:00 PM   


Posts: 50013
Joined: 10.Jan.2001
From: Texas
Status: offline
Hi Beb,

You can't have a firewall with one NIC. [Big Grin]

MS doesn't support this config and neither do I. Too many hidden "issues" that make it unsecure.


(in reply to ::Beblicowcarapis::)
Post #: 2
RE: Firewall with 1 Nic - 5.Aug.2003 10:36:00 AM   


Posts: 2
Joined: 28.Jul.2003
Status: offline
Hi Tom

Now that you mention it, it worked for about a day and then things started going downhill, I reckom I was over optimistic.

Do you reckon we should go for a back to back config ?

Thanks [Frown]

(in reply to ::Beblicowcarapis::)
Post #: 3

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