An ISATAP adapter is a piece of software designed to help organizations transition from the older 32-bit Internet Protocol address infrastructure to the newer 128-bit IP system. Most users will never need or encounter this adapter. Some users with Windows Vista or Windows Server 2008-based computers may experience an error in which the adapter appears as a non-functioning device in Windows Device Manager. In the majority of cases, you can safely disable this device.
The Internet Protocol, or IP, provides a set of standard rules for receiving or sending information online. The older IPv4 protocol, a 32-bit system, is the most widely-used version, but can serve only about 4.3 billion addresses. The newer IPv6 protocol is a 128-bit IP system and can provide many more addresses, but users must transition from one to the other.
ISATAP stands for Intra-Site Automatic Tunnel Addressing Protocol, and acts as a transition mechanism between IPv4 and IPv6. It can transmit both types of packets on an existing IPv4 network. ISATAP adapters were implemented in Microsoft Windows XP and Vista, Linux kernal 2.6.25, Cisco IOS, 6WINDGate and FreeBSD/KAME.
According to Microsoft, some versions of Windows suffer from device driver problems related to the Microsoft ISATAP adapter. The adapter appears in the Device Manager Device list with a yellow exclamation mark next to its name. The properties dialog for the device shows an error message, such as”Windows cannot load driver (Code 31).” This is a confirmed problem with Windows, but Microsoft advises that you ignore it.
Most users do not need the adapter's functionality. If you see an error relating to the ISATAP adapter, you should be able to safely disable the device in Device Manager, or simply leave it alone. If necessary, you can also disable IPv6 entirely in your Network Connections folder. This can make some connections work more efficiently, but will prevent you from joining workgroups and other networks that rely on the IPv6 system.