What Is a Microsoft ISATAP Adapter?

By Kammy Pow

Whenever new technology standards are introduced, there is often a transition period as companies and users begin adopting the new standard and leaving behind the old one. In the case of Internet Protocols, iPv6 was designed to replaced the first publicly available IP, iPv4, in the 1990's. Because the tw versions of IP aren't compatible, Microsoft released its Intra-site Automatic Tunnel Addressing Protocol, or ISATAP, to help facilitate the transition between existing IPv4 networks to the new IPv6 networks. The transition period has proved to be particularly long, since in 2014, iPv4 was still used by over 97 percent of computers connecting to the Internet.


The IPv4 system had been running out of network address spaces, necessitating the expansion of the Internet standard, which came with the development of IPv6. In order to accommodate the change, Microsoft developed the ISATAP interface to allow computers to send iPv6 packets over older networks by encapsulating them with an IPv4 header before transmitting the data.

How It Works

The ISATAP interface creates an IPv6 network address from an IPv4 address, resulting in a dual-stack node. This node views the IPv6 network as a link layer for IPv4 and allows the enterprise's network to transmit IPv4 packets over the IPv6 network. The ISATAP interface also queries the domain name server, or DNS, to build a potential routers list and maintain a viable IPv6 network with which the old IPv4 network can communicate.

Address Formats

IPv4 addresses use a four-byte, 32-bit structure for multicast, private and public networks. The Microsoft ISATAP embeds this four-byte address inside a five-octet, 64-bit header known as EUI-64. Such an address allows for backward compatibility to legacy IPv4 systems, resulting in dual-stacked nodes that can route between IPv4 and IPv6 networks.

Supported Platforms

The Microsoft ISATAP interface supports most Windows operating systems, including versions of Windows XP, Windows Vista, Windows 7, Windows 8, Windows Server 2008, Windows Server 2012 and Windows Mobile. Microsoft has also implemented support of the ISATAP for some versions of Linux and Cisco internetwork operating systems, or IOS.

Twenty Years Later

With the development of ISATAP, security issues that existed in IPv4 networks continue to exist with the new IPv6 standard, such as source address spoofing. In May 2014, Google statistics show that only 3.66 percent of computers connecting to Google servers are using iPv6.