Configure TCP/IP - MCSA Windows Server 2012 R2: Installation and Configuration Study Guide - page 423

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6to4 is a mechanism used to transition to IPv4. This method, like ISATAP, treats
the IPv4 address space as a logical link layer with each IPv6 space in transition
using a 6to4 router to create endpoints using the IPv4 space as a point-to-point
connection (kind of like a WAN, eh?). 6to4 implementations still do not work well
through a NAT, although a 6to4 implementation using an Application layer gate-
way (ALG) is certainly doable.

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Teredo is a mechanism that allows users behind a NAT to access the IPv6 space by
tunneling IPv6 packets in UDP.

Pseudo-interfaces are used in these mechanisms to create a usable interface for the
operating system. Another interesting feature of IPv6 is that addresses are assigned to
interfaces (or pseudo-interfaces), not simply to the end node. Your Windows Server 2012
R2 will have several unique IPv6 addresses assigned.
New Broadcast Methods IPv6 has moved away from using broadcasting. The three
types of packets used in IPv6 are unicast, multicast, and anycast. IPv6 clients then must
use one of these types to get the MAC address of the next Ethernet hop (default gateway).
IPv6 makes use of multicasting for this along with the new functionality called neighbor
discovery. Not only does ARP utilize new functionality, but ICMP (also a layer 3 protocol)
has been redone and is now known as ICMP6. ICMP6 is used for messaging (packet too
large, time exceeded, and so on) as it was in IPv4, but now it's also used for the messaging
of IPv6 mobility. ICMP6 echo request and ICMP6 echo reply are still used for ping.

IPv6 Addressing Concepts

You need to consider several concepts when using IPv6 addressing. For starters, the format
of the address has changed. Three types of addresses are used in IPv6 with some predefined
values within the address space. You need to get used to seeing these addresses and be able
to identify their uses.

IPv6 Address Format
For the design of IPv4 addresses, you present addresses as octets or the decimal (base 10)
representation of 8 bits. Four octets add up to the 32 bits required. IPv6 expands the address
space to 128 bits, and the representation is for the most part shown in hexadecimal (a notation
used to represent 8 bits using the values 0-9 and A-F). Figure 8.13 compares IPv4 to IPv6.
A full IPv6 address looks like this example:

2001:0DB8:0000:0000:1234:0000:A9FE:133E
You can tell the implementation of DNS will make life a lot easier even for those who like
to ping the address in lieu of the name. Fortunately, DNS already has the ability to handle
IPv6 addresses with the use of an AAAA record. ( A is short for alias .) An A record in IPv4's
addressing space is 32 bits, so an AAAA record, or four A is is 128 bits. The Windows Server
2012 R2 DNS server handles the AAAA and the reverse pointer (PTR) records for IPv6.