Managing HP Serviceguard A.11.20.10 for Linux, December 2012

D.1.2 IPv6 Address Prefix
IPv6 Address Prefix is similar to CIDR in IPv4 and is written in CIDR notation. An IPv6 address
prefix is represented by the notation:
IPv6-address/prefix-length where ipv6-address is an IPv6 address in any notation
listed above and prefix-length is a decimal value representing how many of the leftmost
contiguous bits of the address comprise the prefix. Example:
fec0:0:0:1::1234/64
The first 64-bits of the address fec0:0:0:1 forms the address prefix. An address prefix is used
in IPv6 addresses to denote how many bits in the IPv6 address represent the subnet.
D.1.3 Unicast Addresses
IPv6 unicast addresses are classified into different types. They are: global aggregatable unicast
address, site-local address and link-local address. Typically a unicast address is logically divided
as follows:
Table 14
128-n bitsn bits
Interface IDSubnet prefix
Interface identifiers in a IPv6 unicast address are used to identify the interfaces on a link. Interface
identifiers are required to be unique on that link. The link is generally identified by the subnet
prefix.
A unicast address is called an unspecified address if all the bits in the address are zero. Textually
it is represented as “::”.
The unicast address ::1 or 0:0:0:0:0:0:0:1 is called the loopback address. It is used by a
node to send packets to itself.
D.1.4 IPv4 and IPv6 Compatibility
There are a number of techniques for using IPv4 addresses within the framework of IPv6 addressing.
D.1.4.1 IPv4 Compatible IPv6 Addresses
The IPv6 transition mechanisms use a technique for tunneling IPv6 packets over the existing IPv4
infrastructure. IPv6 nodes that support such mechanisms use a special kind of IPv6 addresses that
carry IPv4 addresses in their lower order 32-bits. These addresses are called IPv4 Compatible IPv6
addresses. They are represented as follows:
Table 15
32 bits16 bits80 bits
IPv4 address0000zeros
Example:
::192.168.0.1
D.1.4.2 IPv4 Mapped IPv6 Address
There is a special type of IPv6 address that holds an embedded IPv4 address. This address is used
to represent the addresses of IPv4-only nodes as IPv6 addresses. These addresses are used especially
by applications that support both IPv6 and IPv4. These addresses are called as IPv4 Mapped IPv6
Addresses. The format of these address is as follows:
278 IPv6 Network Support