ISATAP (Intra - Site Automatic Tunnel Addressing Protocol ) is an IPv6 transition mechanism for the transmission of IPv6 packets between dual-stack nodes that are connected via an IPv4 network. In this developed by Cisco and Microsoft variant of the 6to4 mechanism, an automatic tunnel is established, the IPv4 network from the perspective of IPv6 is used as link layer (data link layer in the OSI model ).

The IPv6 address is formed from the local IPv4 address.

The mechanism has been standardized in RFC 5214.


When ISATAP IPv4 address is included in the interface ID of the IPv6 address. For this purpose, a / 128 address is assigned from the normal unicast address space of your provider per IPv4 host.

To generate the address following algorithm is used:

: 0000:5 EFE:


From the IPv4 Address: 91,198,174,225

Derived under the given prefix: 2001:4 CA0: 0: FE00 :: / 64

Following ISATAP address from:

2001:4 CA0: 0: FE00: 0:5 EFE: 91,198,174,225 or

2001:4 CA0: 0: FE00: 0:5 EFE: 5BC6: AEE1

Implementation of ISATAP

ISATAP is implemented in Microsoft Windows XP, Windows Vista, Windows 7, Windows 8, Windows Server 2008, Windows Server 2012, Windows Mobile, Linux, and in some versions of Cisco IOS. On Linux, the userspace program will additionally isatapd needed.


  • RFC 5214, Intra- Site Automatic Tunnel Addressing Protocol ( ISATAP )