Many Windows users ans IT administrators have opted to disable IPv6 to solve Internet connectivity issues, or on the assumption that they are not running any applications or services that use it. Yet others have disabled it because they feel that having both IPv4 and IPv6 enabled, effectively doubled their DNS and Web traffic.
Microsoft explains that this is far from truth. It goes on to explain what are the company’s recommendations about disabling IPv6. But first, let us divert our attention to these standards.
IPv4 is the fourth version in the development of Internet Protocol Internet that routes most traffic on the Internet. The version provides us with 32 bit address. The newer version of IP, that is the IPv6 on the other hand offers us 128 bit addressing capability which means that there would be more number of addresses available for use and making the internet more secure. Check this post to learn more about the difference between IPv4 and IPv6.
IPv6 is a mandatory part of the Windows operating system and it is enabled. Microsoft says its Windows OS was designed specifically with IPv6 present. If IPv6 is disabled on Windows 7 or upper versions, some components such as Remote Assistance, HomeGroup, DirectAccess, and Windows Mail may actually fail to function. The problem gets compounded with a delay in startup time of 5 seconds or more, if IPv6 is disabled.
Disabling IPv6 delayed boot times by 5 seconds
For years, the method practiced regularly to disable IPv6 was setting the DisabledComponents value at 0xFFFFFFFF under the following registry key:
However, disabling IPv6 with the above registry value caused a 5 second boot delay in the Pre-Session Init Phase of OS startup.
The reason for the delay is that underlying code requires the upper 24-bits to be zero. Since the upper 24-bits have no meaning, setting a value of 0xFF is functionally identical to the 0xFFFFFFFF setting. Unfortunately, the DisabledComponents setting got documented with an all “F” bitmask. If you used this documented setting this unnecessarily results in a 5 second boot delay, says Microsoft.
The Windows versions impacted by the 5 second boot delay include Windows Vista, Windows 7, Windows 8, Windows 8.1, Windows Server 2008, Server Windows Server 2008 R2, Windows Server 2012 and Windows Server 2012 R2.
Correct way to disable IPv6
Now a 5 second boot delay may not matter on servers that rarely reboot, but on client operating systems, especially those that are configured with SSD disk drives where full OS boot times are approaching 30 seconds – it does matter!
Leaving IPv6 enabled on current Windows client and server operating systems remains the best practice configuration.
But if you do wish to disable IPv6, the correct setting to use in environments that legitimately need to disable IPv6 and IPv6 transition technologies is to configure the DisabledComponents registry key with a value of 0xFF, says Microsoft now.
If you have disabled IPv6 by setting DisabledComponents at 0xFFFFFFFF, it might be a good idea to make the change based on these new findings.
Both the Fix IT and the manual steps mentioned in KB929852 have been updated to reflect this change.