222 Understanding IPv6, Second Edition

Hosts File

The Hosts file stored in the %SystemRoot%\System32\Drivers\Etc folder supports static entries for IPv6 addresses. Each entry must be of the following form:

Address Name

Address is an IPv6 address, and Name is a name associated with the address. The address and name are not case sensitive and must be separated by at least one space or tab character.

The following is an example entry:

2001:db8:6c2b:f282:DD48:AB34:D07C:3914 ipv6test

The entries in the Hosts file are automatically loaded into the DNS resolver cache. You cannot specify a zone ID (also known as a scope ID) as part of the address. If you put entries for linklocal addresses in the Hosts file, the IPv6 protocol will select a zone ID for the

destination traffic to the resolved link-local address.

DNS Resolver

The DNS resolver, which is part of the DNS Client service in Windows Server 2008 and Windows Vista that queries for DNS names and processes the results, supports the processing of both A and AAAA records in DNS query responses.

The DNS resolver supports queries and responses over IPv6 when the IPv6 addresses of DNS servers have been configured. By default, DNS resolvers are configured with the well-known site-local IPv6 addresses of FEC0:0:0:FFFF::1, FEC0:0:0:FFFF::2, and FEC0:0:0:FFFF::3 as DNS server IPv6 addresses. If you have deployed DNS servers at these addresses and provided reachability to these servers in your routing infrastructure, no other configuration of DNS resolvers is needed. However, in many cases, network administrators will want to place DNS servers in strategic locations on the network and configure the DNS resolvers with their global or unique local addresses.

You can configure Windows Server 2008 and Windows Vista for the addresses of IPv6enabled DNS servers with the following methods:

■Through the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) and the DNS Recursive Name Server option that is defined in RFC 3646. For more information about DHCPv6, see Chapter 8.

■From the DNS tab for the properties of the Internet Protocol Version 6 (TCP/IPv6) component from the properties of a connection in the Network Connections folder.

■With the netsh interface ipv6 add dnsserver command.

DNS Server Service

The DNS Server service in Windows Server 2008 supports the manual creation and DNS dynamic update of AAAA and PTR records. To manually create an AAAA record for the Windows Server 2008 DNS Server service, do the following:

1.Run the DNS snap-in from the Administrative Tools folder.

2.Right-click the zone in which the record is to be stored, and click New Host (A Or AAAA).

3.In the New Host dialog box, type the host name and the IPv6 address, and then click Add Host.

Figure 9-4 shows an example of adding an AAAA record with the New Host dialog box.

Figure 9-4 The New Host dialog box for AAAA records

For DNS dynamic update, the zones in which records are dynamically updated by DNS clients must be configured to allow dynamic updates. For the Windows Server 2008 DNS Server service, you can enable dynamic updates when the zone file is created with the New Zone Wizard or from the General tab for the properties of the zone.

Reverse lookup zones for IPv6-based PRT records can be automatically created when a computer running Windows Server 2008 uses DNS dynamic update to register its PTR record. You can also manually create reverse lookup zones for IPv6-based PRT records with the following:

1.From the console tree of the DNS snap-in, right-click Reverse Name Lookup Zones, and then click New Zone.

2.On the Welcome To The New Zone Wizard page of the New Zone Wizard, click Next.

3.On the Zone Type page, select the appropriate zone type (primary, secondary, or stub) and then click Next.

224Understanding IPv6, Second Edition

4.If you have not installed and configured Active Directory proceed to step 5; otherwise, on the Active Directory Zone Replication page, select the appropriate zone replication behavior and then click Next.

5.On the Reverse Lookup Zone Name page, click IPv6 Reverse Lookup Zone and then click Next.

6.On the Reverse Lookup Zone Name page, type the IPv6 address prefix of the zone (including the prefix length) and then click Next. The following figure shows an example:

7.If the new primary zone is not integrated into Active Directory, on the Zone File page, select the appropriate method to create a new zone file or use an existing file, specify the file name, and then click Next.

8.On the Dynamic Update page, select the appropriate dynamic update behavior and then click Next.

9.On the Completing The New Zone Wizard page, click Finish.

The Windows Server 2008 DNS Server service by default supports DNS traffic over IPv6, including name queries and dynamic updates.

DNS Dynamic Update

Windows Server 2008 and Windows Vista support DNS dynamic update to automatically register AAAA records over either IPv4 or IPv6 for the following addresses:

■Global addresses with random or EUI-64 IDs (public addresses), and global addresses with ISATAP-derived interface IDs.

■Unique local addresses with random, EUI-64, and ISATAP-derived interface IDs.

■Site-local addresses with random, EUI-64, and ISATAP-derived interface IDs.

Temporary addresses (short-lived global addresses with randomly derived interface IDs), 6to4 addresses assigned to the 6to4 tunnel interface (by default), Teredo addresses

(by default), the loopback address, and link-local addresses are not registered with DNS.

DNS dynamic update for IPv6 for connections in the Network Connections folder is controlled by the Register This Connection’s Address In DNS check box on the DNS tab from the advanced settings of the Internet Protocol Version 6 (TCP/IPv6) protocol. This check box is enabled by default.

Computers running Windows Server 2008 register PTR records for host names in the IP6.ARPA reverse domain. Computers running Windows Vista register PTR records for host names in the IP6.ARPA reverse domain for stateless addresses. You can configure PRT records manually for the Windows Server 2008 DNS Server service by adding PTR records to the appropriate zone files using the DNS snap-in.

Source and Destination Address Selection

IPv6 in Windows Server 2008 and Windows Vista support the source and destination address selection algorithms described in RFC 2874 with the following exceptions:

■Windows Vista prefers the use of temporary addresses over public addresses.

■Windows Vista uses a global scope for both public and private IPv4 addresses.

You can modify the default preference behavior for IPv6 address prefixes by changing the entries in the prefix policy table. You can view the prefix policy table with the netsh interface ipv6 show prefixpolicies command. The following is an example of the default prefix policy table:

The entries in this table correspond to the following types of IPv6 traffic:

■Prefix ::1/128 is for the loopback address.

■Prefix ::/0 is for all IPv6 traffic.

■Prefix 2002::/16 is for 6to4 traffic.

■Prefix ::/96 is for IPv4-compatible traffic (deprecated).

■Prefix ::ffff:0:0/96 is for IPv4-mapped traffic.

■Prefix 2001::/32 is for Teredo traffic.