Why to Disable IPv6 Techspot primarily caters to home users, where the LAN is behind a simple 4-8 port router with few devices. Most of our systems are Pre-Vista and have no support for IPv6 Almost all of our devices (eg: printers, printservers, routers) don't have ipv6 support IPv6 is more complicated to administer and configure IPv6 tunneling of IPv4 data presents a security exposure HOW to Disable IPv6 Windows XP: Start->Run->cmd /k ipv6 uninstall Unlike Windows XP, IPv6 in Windows Vista cannot be uninstalled. To disable IPv6 on a specific connection, you can go to the Network Connections folder, obtain properties of the connection and clear the check box next to the Internet Protocol version 6 (TCP/IPv6) component in the list. This method disables IPv6 on your LAN interfaces and connections, but does not disable IPv6 on tunnel interfaces or the IPv6 loopback interface. To selectively disable IPv6 components and configure behaviors for IPv6 in Windows Vista, create and configure the following registry value (DWORD type) Code: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tcpip6\Parameters add DWORD [B]DisabledComponents [/B] set to 0 by default. The DisabledComponents registry value is a bit mask that controls the following series of flags, starting with the low order bit (Bit 0): * Bit 0 Set to 1 to disable all IPv6 tunnel interfaces, including ISATAP, 6to4, and Teredo tunnels. Default value is 0 * Bit 1 Set to 1 to disable all 6to4-based interfaces. Default value is 0 * Bit 2 Set to 1 to disable all ISATAP-based interfaces. Default value is 0 * Bit 3 Set to 1 to disable all Teredo-based interfaces. Default value is 0 * Bit 4 Set to 1 to disable IPv6 over all non-tunnel interfaces, including LAN interfaces and *Point-to-Point Protocol (PPP)-based interfaces. Default value is 0 * Bit 5 Set to 1 to modify the default prefix policy table to prefer IPv4 to IPv6 when attempting connections. Default value is 0 To determine the value of DisabledComponents for a specific set of bits, construct a binary number consisting of the bits and their values in their correct position and convert the resulting number to hexadecimal. For example, if you want to disable 6to4 interfaces, disable Teredo interfaces, and prefer IPv4 to IPv6, you would construct the following binary number: 101010. When converted to hexadecimal, the value of DisabledComponents is 0x2A. The following table lists some common configuration combinations and the corresponding value of DisabledComponents. Configuration combination DisabledComponents value Disable all tunnel interfaces 0x1 Disable 6to4 0x2 Disable ISATAP 0x4 Disable Teredo 0x8 Disable Teredo and 6to4 0xA Disable all LAN and PPP interfaces 0x10 Disable all LAN, PPP, and tunnel interfaces 0x11 Prefer IPv4 over IPv6 0x20 Disable IPv6 over all interfaces and prefer IPv4 to IPv6 0xFF You must restart the computer for the changes to the DisabledComponents registry value to take effect.