Windows 7 / Networking

Understanding Address Autoconfiguration

On IPv4 networks, addresses can be assigned to hosts in three ways:

  • Manually, using static address assignment
  • Automatically, using Dynamic Host Configuration Protocol (DHCP) if a DHCP server is present on the subnet (or a DHCP relay agent is configured on the subnet)
  • Automatically, using APIPA, which randomly assigns the host an address from the range to with subnet mask

On IPv6 networks, static addresses are generally assigned only to routers and (sometimes) servers, but hardly ever to client computers. Instead, IPv6 addresses are almost always assigned automatically using a process called address autoconfiguration. Address autoconfiguration can work in three ways: stateless, stateful, or both. Stateless address autoconfiguration is based on the receipt of ICMPv6 Router Advertisement messages. Stateful address autoconfiguration, on the other hand, uses DHCP for IPv6 (DHCPv6) to obtain address information and other configuration settings from a DHCPv6 server.

Note The DHCP Server service of Windows Server 2008 supports DHCPv6. The DHCP Server service of Windows Server 2003 does not support DHCPv6.

All IPv6 nodes (hosts and routers) automatically assign themselves link-local addresses (addresses having the address prefix FE80::/64); this is done for every interface (both physical and logical) on the node. (6to4 interfaces are an exception-they might not have link-local addresses automatically assigned.) These autoconfigured link-local addresses can be used only to reach neighboring nodes (nodes on the same link). When specifying one of these addresses as a destination address, you might need to specify the zone ID for the destination. In addition, link-local addresses are never registered in DNS servers.

Note Manual assignment of IPv6 addresses is generally needed only for IPv6 routers and for some servers. You can configure a computer running Windows 7 with multiple interfaces to be used as a router. For more information on configuring IPv6 routers, see the Cable Guy article titled "Manual Configuration for IPv6" at For a description of the IPv6 routing table, see the Cable Guy article titled "Understanding the IPv6 Routing Table" at

An autoconfigured IPv6 address can be in one or more of the states shown in Table-6.

Table-6 Possible States for an Autoconfigured IPv6 Address

TentativeThe uniqueness of the address is still being verified using duplicate address detection.
ValidThe address is unique and can now send and receive unicast IPv6 traffic until the Valid Lifetime expires.
PreferredThe address can be used for unicast traffic until the Preferred Lifetime expires.
DeprecatedThe address can still be used for unicast traffic during existing communication sessions, but its use is discouraged for new communication sessions.
InvalidThe Valid Lifetime for the address has expired and it can no longer be used for unicast traffic.

Note The Valid and Preferred Lifetime for stateless autoconfigured IPv6 addresses is included in the Router Solicitation message.

For detailed descriptions of how address autoconfiguration, address resolution, router discovery, redirect, duplicate address detection, and neighbor unreachability detection processes are performed, see the white paper, "Introduction to IP Version 6," at

Note To display the state for each autoconfigured IPv6 address on a Windows 7 computer, open a command prompt and type netsh interface ipv6 show addresses at a command prompt.

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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