While
IPv4 is still a widely used standard and most of our examples focus
primarily on IPv4, in installing and configuring server roles, we do
give attention to the IPv6 standard. Therefore, it is beneficial to be
aware of what IPv6 is and how it will affect you today and going
forward in the network.
IPv6
was introduced as a means of addressing the shortcomings of its
predecessor, IPv4. The following are some of the advantages of IPv6:
Larger address space: IPv6 uses a 128-bit address space (3.4 × 1038
available address combinations), making it expandable to virtually
indefinite levels. This large address space also allows you to arrange
address spaces into multilevel subnets.
Security:
The absence of NAT means IPv6 can implement end-to-end IPSec. IPSec
support is not optional (as it is in IPv4); it is required, greatly
improving security.
Better efficiency: IPv6 involves reduced header information and better support for QOS. In addition, fragmentation is handled by the sending host.
Of
course, the enhancements come with some changes. IPv6 addresses use
16-bit blocks that are represented by four-digit hexadecimal numbers.
An IPv6 address is broken down into three parts: the site prefix (48
bits), the subnet ID (16 bits), and the interface ID (64 bits). Figure 1 shows an example of an IPv6 address.
This
is a big change from the four-digit integers of IPv4, but it is not the
only change. The structure of classes, public/private networks,
stateful and stateless addressing, and header information have also
changed.
IPv6 categorizes addresses by type and scope. IPv6 uses the following three address types:
Unicast: A packet is delivered to a single interface.
Multicast: A packet is delivered to multiple interfaces. Broadcasts are not used and have been replaced with multicast.
Anycast: A packet is delivered to the nearest multiple interfaces.
IPv6 categorizes addresses by the following scopes:
Global:
This scope begins with a prefix of 2 or 3 (for example, 3FFE) that can
be used over the Internet. It is assigned by an ISP or the registry.
Unique local: This scope begins with a prefix of FC or FD (for example, FD00) and is used in internal (private) networks.
Link local:
This scope begins with the prefix FE80, is automatically assigned by
the OS, is usable only within a subnet, and is not routable.
In
addition to these three scopes, scopes exist for special addresses such
as loopback addresses. One notable scope is the 6to4 address scope,
which uses the 2002 prefix. This scope is designated for converting
IPv4 addresses to IPv6 addresses.
Other
features are neighbor discovery, which allows a client to announce its
existence to its neighbor in a subnet. Stateless address configuration
allows a client to automatically configure itself with an IP address
(link-local), using prefix discovery from the router. IPv6 can easily
be extended for new functions.
In
Windows Server 2008, you can use either IPv4 or IPv6. The advantages of
IPv6 make it a highly attractive option. However, the lack of adoption,
the learning curve involved, and the fact that you can still use IPv4
make many administrators consider IPv6 more of future consideration.
Going forward from Windows Server 2008, IPv6 will become more the
standard rather than an option, as it is now. The need to address the
lack of available IP addresses for the Internet makes it important to
understand how to implement this new standard.
