Managing HP Serviceguard for Linux Ninth Edition, April 2009

D IPv6 Network Support
This appendix describes some of the characteristics of IPv6 network addresses,
specifically:
• IPv6 Address Types
• Network Configuration Restrictions (page 321)
• Configuring IPv6 on Linux (page 322)
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 D-1 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Unlike IPv4, IPv6 has no broadcast addresses; their functions are superseded by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.
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
IPv6 Address Types 317