Windows 7 / Networking

Understanding Name Queries

Because the dual-layer TCP/IP stack in Windows 7 means that both IPv4 and IPv6 are enabled by default, DNS name lookups by clients running Windows 7 can involve the use of both A and AAAA records. (This is true only if your name servers support IPv6, which is the case with the DNS Server role for Windows Server 2008 and Windows Server 2003.) By default, the DNS client in Windows 7 uses the following procedure when performing a name lookup using a particular interface:

  1. The client computer checks to see whether it has a non-link-local IPv6 address assigned to the interface. If it has no non-link-local addresses assigned, the client sends a single name lookup to the name server to query for A records and does not query for AAAA records. If the only non-link-local address assigned to the interface is a Teredo address, the client again does not query for AAAA records. (The Teredo client in Windows Vista and later versions is explicitly built not to automatically perform AAAA lookups or register with DNS to prevent overloading of DNS servers.)
  2. If the client computer has a non-link-local address assigned to the interface, the client sends a name lookup to query for A records.
    • If the client then receives a response to its query (not an error message), it follows with a second lookup to query for AAAA records.
    • If the client receives no response or receives any error message (except for Name Not Found), it does not send a second lookup to query for AAAA records.

Note Because an interface on an IPv6 host typically has multiple IPv6 addresses, the process by which source and address selection works during a name query is more complex than when DNS names are resolved by IPv4 hosts. For a detailed description of how source and address selection works for IPv6 hosts, see the Cable Guy article titled "Source and Destination Address Selection for IPv6" at For additional information on DNS behavior in Windows 7 and Windows Vista, see "Domain Name System Client Behavior in Windows Vista" at For information about the different types of IPv6 addresses usually assigned to an interface, see the section titled "Configuring and Troubleshooting IPv6 in Windows 7" later in this tutoriak.

Note Issues have arisen with poorly configured DNS name servers on the Internet. These issues, which are described in RFC 4074 (, do not cause problems on Windows Vista or later versions because Microsoft has altered the DNS client behavior specifically to compensate for them. However, administrators of DNS servers should make sure these issues are fixed, because they can cause problems with DNS name resolution for most IPv6 networking stacks, including stacks found in earlier Windows platforms such as Windows XP.

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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