Combined ISATAP and 6to4 tunneling mechanisms allow to easily interconnecting IPv6 and IPv4 nodes over an existing IPv4 architecture. As such, it could largely be used as a first step deployment towards IPv6.
A key advantage of the 6to4 mechanism is that a customer can use IPv6 without the need of any global IPv6 prefix allocated by an ISP or any other service provider. Only a valid, globally unique 32-bit IPv4 address is necessary. Moreover, 6to4 requires fewer configurations than configured tunnels.
ISATAP hosts do not require any manual configuration and create ISATAP addresses using standard address auto configuration mechanisms. ISATAP can be used for communication between IPv6/IPv4 nodes on an IPv4 network.
The combination of these two mechanisms brings a transition mechanism that is powerful and easy to configure.
Using 6to4 enables 6to4 hosts (meaning that at least one 6to4 address has been configured) to communicate with other 6to4 hosts located on the same site, and also with 6to4 hosts located in other sites on the IPv4 Internet thanks to 6to4 routers. It also enables the communication with IPv6 native hosts connected for instance to the 6bone thanks to a 6to4 relay router. To do so, 6to4 uses a public IPv4 address to create the 64-bit identifier portion of an IPv6 address. The full address of a 6to4 node is:
2002:WWXX:YYZZ:[SLA ID]:[Interface ID]
where 2002 is the TLA ID reserved to 6to4 addresses, and WWZZ:YYZZ corresponds to the colon-hexadecimal representation of an IPv4 address.
Local routers advertise the 6to4 prefixes and hosts use them to build an auto-configured 6to4 address. Additionally, a 2002::/16 route is used to tunnel the IPv6 traffic to other 6to4 hosts outside the local network. This traffic is forwarded to the 6to4 router located at the border of the IPv6 site. The 6to4 router then encapsulates the traffic in an IPv4 header and sends it to the destination IPv4 address that is embedded in the right portion of the 6to4 address. At the other side, the IPv6 packet is decapsulated and forwarded to the appropriate node.
ISATAP can also be used for communication between IPv4/IPv6 nodes through an IPv4 network. The full format of an ISATAP identifier is:
::0:5EFE:w.x.y.z
where 0:5EFE is the combination of a reserved OUI (Organizationally Unique Identifier) and a type indicating an embedded IPv4 address ; and where w.x.y.z. is a unicast public or private IPv4 address in decimal.
The ISATAP interface identifier can be combined with any 64 bits prefix including 6to4 prefixes to build an IPv6 address.
A key advantage of the 6to4 mechanism is that a customer can use IPv6 without the need of any global IPv6 prefix allocated by an ISP or any other service provider. Only a valid, globally unique 32-bit IPv4 address is necessary. Moreover, 6to4 requires fewer configurations than configured tunnels.
ISATAP hosts do not require any manual configuration and create ISATAP addresses using standard address auto configuration mechanisms. ISATAP can be used for communication between IPv6/IPv4 nodes on an IPv4 network.
The combination of these two mechanisms brings a transition mechanism that is powerful and easy to configure.
Using 6to4 enables 6to4 hosts (meaning that at least one 6to4 address has been configured) to communicate with other 6to4 hosts located on the same site, and also with 6to4 hosts located in other sites on the IPv4 Internet thanks to 6to4 routers. It also enables the communication with IPv6 native hosts connected for instance to the 6bone thanks to a 6to4 relay router. To do so, 6to4 uses a public IPv4 address to create the 64-bit identifier portion of an IPv6 address. The full address of a 6to4 node is:
2002:WWXX:YYZZ:[SLA ID]:[Interface ID]
where 2002 is the TLA ID reserved to 6to4 addresses, and WWZZ:YYZZ corresponds to the colon-hexadecimal representation of an IPv4 address.
Local routers advertise the 6to4 prefixes and hosts use them to build an auto-configured 6to4 address. Additionally, a 2002::/16 route is used to tunnel the IPv6 traffic to other 6to4 hosts outside the local network. This traffic is forwarded to the 6to4 router located at the border of the IPv6 site. The 6to4 router then encapsulates the traffic in an IPv4 header and sends it to the destination IPv4 address that is embedded in the right portion of the 6to4 address. At the other side, the IPv6 packet is decapsulated and forwarded to the appropriate node.
ISATAP can also be used for communication between IPv4/IPv6 nodes through an IPv4 network. The full format of an ISATAP identifier is:
::0:5EFE:w.x.y.z
where 0:5EFE is the combination of a reserved OUI (Organizationally Unique Identifier) and a type indicating an embedded IPv4 address ; and where w.x.y.z. is a unicast public or private IPv4 address in decimal.
The ISATAP interface identifier can be combined with any 64 bits prefix including 6to4 prefixes to build an IPv6 address.
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