Managing HP Serviceguard A.11.20.20 for Linux, March 2014

D IPv6 Network Support
This appendix describes some of the characteristics of IPv6 network addresses, specifically:
• IPv6 Address Types
• Network Configuration Restrictions (page 292)
• Configuring IPv6 on Linux (page 292)
D.1 IPv6 Address Types
Several IPv6 types of addressing schemes are specified in the RFC 2373 (IPv6 Addressing
Architecture). IPv6 addresses are 128-bit identifiers for interfaces and sets of interfaces. There are
various address formats for IPv6 defined by the RFC 2373. IPv6 addresses are broadly classified
as unicast, anycast, and multicast.
The following table explains the three types.
Table 17 IPv6 Address Types
An address for a single interface. A packet sent to a unicast address is delivered to the interface
identified by that address.
Unicast
An address for a set of interfaces. In most cases these interfaces belong to different nodes. A
packet sent to an anycast address is delivered to one of these interfaces identified by the address.
Since the standards for using anycast addresses are still evolving, they are not supported in Linux
at present.
Anycast
An address for a set of interfaces (typically belonging to different nodes). A packet sent to a
multicast address will be delivered to all interfaces identified by that address.
Multicast
Unlike IPv4, IPv6 has no broadcast addresses; their functions are superseded by multicast.
D.1.1 Textual Representation of IPv6 Addresses
There are three conventional forms for representing IPv6 addresses as text strings:
• The first form is x:x:x:x:x:x:x:x, where the x’s are the hexadecimal values of the eight
16-bit pieces of the 128-bit address. Example:
2001:fecd:ba23:cd1f:dcb1:1010:9234:4088.
• Some of the IPv6 addresses may contain a long strings of zero bits. In order to make it easy
for representing such addresses textually a special syntax is available. The use of “::” indicates
that there are multiple groups of 16-bits of zeros. The “::” can appear only once in an address
and it can be used to compress the leading, trailing, or contiguous sixteen-bit zeroes in an
address. Example:
fec0:1:0:0:0:0:0:1234 can be represented as fec0:1::1234.
• In a mixed environment of IPv4 and IPv6 nodes an alternative form of IPv6 address will be
used. It is x:x:x:x:x:x:d.d.d.d, where the x’s are the hexadecimal values of higher
order 96 bits of IPv6 address and the d’s are the decimal values of the 32-bit lower order
bits. Typically IPv4 Mapped IPv6 addresses and IPv4 Compatible IPv6 addresses will be
represented in this notation. These addresses are discussed in later sections.
Examples:
0:0:0:0:0:0:10.1.2.3
and
::10.11.3.123
D.1 IPv6 Address Types 289