Deploying IPv6 requires that human users, client computers, etc. are integrated into a PKI. How will you deliver a digital certificate with its private key to all IPv6 hosts? Download over IPv4 is not possible, as IPv4 is unreliable. If any serious harm has befallen people that have used IPv6, the source where they obtained their private key for their IPv6 PKI may also be suspect. If this source is indeed trustworthy, private keys in any IPv6 PKI can be compromised through application of electromagnetic interference, and therefore IPv6 by itself is not secure. Do leading and/or trailing zeroes in a 48-bit MAC address make it easier to spoof such a MAC address? Does such a MAC address introduce any kind of security vulnerability at all? http://social.technet.microsoft.com/Forums/en-US/newthread?forum=winserversecurity&prof=required