Preferring IPv4 over IPv6
What effect will the value 0x21 have when it is assigned to a newly created DisabledComponents registry value on a Windows computer?
Quick check answer
The hexadecimal number 0x21 converted to binary form is 00100001, which means that bits 0 and 5 have the value 1. Assigning this value to the DisabledComponents registry value will do two things. First, it will cause IPv4 to be preferred over IPv6 when the computer attempts to establish network communications. And second, it will disable all IPv6 tunnel interfaces on the computer.
The above tip was excerpted from Mitch Tulloch's book Training Guide: Installing and Configuring Windows Server 2012 from Microsoft Press.
Mitch is a ten-time recipient of the Microsoft Most Valuable Professional (MVP) award and a widely recognized expert on Windows Server and cloud computing technologies. For more information see http://www.mtit.com.