Guess I'm too late for this discussion.

I'm having a meeting today on just this topic to setup secure communication using IPSEC for some critical systems that can not run antivirus software.

For those interested though, Microsoft has even recently published an article on this very topic as well.

Server and Domain Isolation Using IPsec and Group Policy

Step-by-Step Guide to Internet Protocol Security (IPSec)

Windows XP - Internet Protocol security (IPSec)

Might also want to take a look at this page for another possible idea. I've not tested it though for the purposes for which you're looking to do.

Configuring ICMP Router Discovery

Edited by NTDOC (2005-04-14 10:00 PM)