Turning IPv6 Off

 If your organization isn't using IPv6, or any applications that demand it, you may find that your Longhorn boxes are using a bit more network bandwidth than necessary. In fact, the inventor of DNS, Paul Mockapetris, made some fairly strong statements about this effect shortly after Vista debuted. While many observers felt that his criticisms were exaggerated, the guy invented DNS, for Pete's sake, so there's probably some truth in what he says.

Turning IPv6 off isn't as easy as it should be. You can deselect it from the network interface's property sheet, but that doesn't completely turn off IPv6, it just disables it for that interface. The Registry key HKLM\System\CurrentControlSet\Services\tcpip6\parameters is where you need to point REGEDIT, then create a DWORD value named DisabledComponents (if it doesn't already exist) in that key. Set the value for DisabledComponents to 0xFFFFFFFF, restart the machine, and you will have turned off IPv6 for all interfaces. (Change the value to 0x00 if you want to turn IPv6 back on later.) You could deploy this Registry setting via Group Policy to make the change for all your machines.

Microsoft has gone on record as recommending against the step of turning IPv6 off. Personally, I like the idea of turning things off that I'm not using. Anybody who has run into issues turning off IPv6 is invited to comment.

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