Possible States for an Autoconfigured IPv6 Address in Visual C#.NET

Print Denso QR Bar Code in Visual C#.NET Possible States for an Autoconfigured IPv6 Address

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

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 http://www.microsoft.com/downloads/details.aspx FamilyID=CBC0B8A3-B6A4-4952-BBE6D976624C257C&displaylang=en .

To display the state for each autoconfigured Ipv6 address on a Windows 7 computer,

The Domain Name System (DNS) is fundamental to how name resolution works on both IPv4 and IPv6 networks . On an IPv4 network, host (A) records are used by name servers (DNS servers) to resolve fully qualified domain names (FQDNs) like server1.contoso.com into their associated IP addresses in response to name lookups (name queries) from DNS clients . In addition, reverse lookups in which IP addresses are resolved into FQDNs are supported by using pointer (PTR) records in the in-addr.arpa domain . Name resolution works fundamentally the same way with IPv6, with the following differences:

Host records for IPv6 hosts are AAAA ( quad-A ) records, not A records . The domain used for reverse lookups of IPv6 addresses is ip6.arpa, not in-addr.arpa.

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:

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 .) 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 .

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 http://technet.microsoft.com/en-us/library /bb877985.aspx. For additional information on DNS behavior in Windows 7 and Windows Vista, see Domain Name System Client Behavior in Windows Vista at http://technet.microsoft.com/en-us/library/bb727035.aspx. 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 chapter.