Windows Registry Editor Version 5.00

Copy and paste this into a text file, rename it with the extension .reg, and import it; Only registry entries will be imported, the text is ignored.

Teredo in Windows is a transition technology that allows communication between two IP protocols “IPv4” and “IPv6.” The protocols are present on the internet but sometimes need a transition technology like Teredo to communicate. But unfortunately, Teredo can cause DNS leaks (in vpn).
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\tunnel]
"start"=dword:00000004

Avoid Security risks of IPv6, limit your protocal use to Hardened IPv4 as much as possible
Disabled & Hardened TCPIP6 & Components
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\TCPIP6]
"start"=dword:00000004

Totally disabling TCPIp6 System Wide
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\TCPIP6\Parameters]
"DisabledComponents"=dword:000000ff
"DisableIPSourceRouting"=dword:00000002
"EnableICSIPv6"=dword:00000000

IPv6 Helper Service offers IPv6 connectivity over an IPv4 Network
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iphlpsvc]
"start"=dword:00000004

Disable Dhcpv6
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WINEVT\Channels\Microsoft-Windows-Dhcpv6-Client/Admin]
"Enabled"=dword:00000000
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WINEVT\Channels\Microsoft-Windows-Dhcpv6-Client/Operational]
"Enabled"=dword:00000000