The computer that you are installing ISA Server on, of course, must be multi-homed, or have multiple network interface cards installed in it, in order for it to be connected to multiple networks and used as a firewall. One adapter for each network the server will connect to is necessary, but at least one adapter for the internal network, and one for the external network should be installed. Additionally, the external network connection can be a modem as well for dial-up connectivity.
ISA Server 2004 Enterprise Edition requires a little bit above and beyond the minimum listed above. In addition to the above requirements, Enterprise Edition also needs about 352 MB of additional space to run these components: ISA Server Services, Configuration Storage Server, and ISA Server Management.
With that said, you should try to find a much better server than the one listed above to make sure that you have a box capable of running ISA effectively. The minimum requirements may suffice for a small branch office or workgroup-sized network, but anything larger than that may need some stronger hardware. As with most products in the computer business, more processing power, more RAM, and more hard disk space is better.
As far as server operating systems go, ISA Server can run on both Windows 2000 Server and Windows Server 2003 platforms, with a few caveats. First, only Standard Edition can run on a Windows 2000 Server platform. Enterprise Edition requires a Windows Server 2003 operating system to run on. Second, the Windows 2000 box that you install Standard Edition on must have at least Service Pack 4 installed on it, as well as Internet Explorer 6. Other than those requirements, you should always, of course, ensure that the operating system you are installing the ISA server on has been updated with the most current hotfixes and patches, to ensure that you are getting the latest security and operating system fixes available.
That closes out our two part series on planning. In the next article, we’ll get to the part that most folks love better than planning, which is actually popping the CD in and installing ISA Server 2004. Until then, keep your users happy and your networks secure!