Windows 7 / Networking

Understanding ISATAP

By default, the IPv6 protocol in Windows 7 automatically configures a link-local unicast IPv6 address of the form FE80::5EFE:w.x.y.z (for private IPv4 addresses) or FE80::200:5EFE:w.x.y.z (for public IPv4 addresses). This address is a link-local ISATAP address, and it is assigned to the ISATAP tunneling interface. Using their link-local ISATAP addresses, two ISATAP hosts (such as computers running Windows 7) can communicate using IPv6 by tunneling across an IPv4- only network infrastructure (such as a network whose routers forward only IPv4 packets and not IPv6 packets).

Note In Windows 7 and in Windows Vista SP1 or later versions, link-local ISATAP addresses are automatically configured only if the name "ISATAP " (the ISATAP router name) can be resolved. Otherwise, the ISATAP interface will be media disconnected. However, if you administratively enable ISATAP by using the netsh interface isatap set state enabled command, the link-local address will be configured regardless of whether the ISATAP router name can be resolved.

With the addition of one or more ISATAP routers (IPv6-enabled routers that advertise address prefixes, forward packets between ISATAP hosts and other ISATAP routers, and act as default routers for ISATAP hosts), a variety of transition topologies become possible, including:

  • Connecting ISATAP hosts on an IPv4-only intranet to an IPv6-capable network.
  • Connecting multiple "islands" of ISATAP hosts through an IPv6-capable backbone.

These configurations are possible because ISATAP routers advertise address prefixes that enable ISATAP hosts (such as computers running Windows 7) to autoconfigure global or unique local unicast IPv6 addresses.

Note Without the presence of an ISATAP router, ISATAP hosts running Windows Vista RTM could only autoconfigure link-local unicast IPv6 addresses, which limited IPv6 communications to those between hosts on the IPv4-only intranet. This was changed in Windows Vista SP1 so that without an ISATAP router, the interface will show media disconnected. In other words, Windows Vista SP1 won't configure a link-local ISATAP address when no ISATAP router is configured. The behavior in Windows 7 is the same as in Windows Vista SP1.

Note For more information on how ISATAP works, see the white paper, "IPv6 Transition Technologies," at &displaylang=en.

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In this tutorial:

  1. Deploying IPv6
  2. Understanding IPv6
  3. Understanding IPv6 Terminology
  4. Understanding IPv6 Addressing
  5. Understanding IPv6 Prefixes
  6. Understanding IPv6 Address Types
  7. Understanding Unicast Addresses
  8. Identifying IPv6 Address Types
  9. Understanding Interface Identifiers
  10. Comparing IPv6 with IPv4
  11. Understanding IPv6 Routing
  12. How IPv6 Routing Works
  13. IPv6 Route Determination Process
  14. IPv6 Routing Table Structure
  15. Understanding ICMPv6 Messages
  16. Understanding Neighbor Discovery
  17. Understanding Address Autoconfiguration
  18. Understanding Name Resolution
  19. Understanding Name Queries
  20. Understanding Name Registration
  21. PTR Records and IPv6
  22. IPv6 Enhancements in Windows 7
  23. Summary of IPv6 Enhancements in Windows 7
  24. Configuring and Troubleshooting IPv6 in Windows 7
  25. Configuring IPv6 in Windows 7 Using the User Interface
  26. Configuring IPv6 in Windows 7 Using Netsh
  27. Other IPv6 Configuration Tasks
  28. Enabling or Disabling IPv6
  29. Disabling Random Interface IDs
  30. Resetting IPv6 Configuration
  31. Displaying Teredo Client Status
  32. Troubleshooting IPv6 Connectivity
  33. Planning for IPv6 Migration
  34. Blocking Teredo
  35. Understanding ISATAP
  36. Migrating an Intranet to IPv6
  37. Step 1: Upgrading Your Applications and Services
  38. Step 2: Preparing Your DNS Infrastructure
  39. Step 3: Upgrading Your Hosts
  40. Step 4: Migrating from IPv4-only to ISATAP
  41. Step 5: Upgrading Your Routing Infrastructure
  42. Step 6: Upgrading Your DHCP Infrastructure
  43. Step 7: Migrating from ISATAP to Native IPv6
  44. The Advantages of IPv6
  45. Address Resolution in IPv6