Operation Manual

DenitionPrex (hex)
Site-local addresses. These may be
routed, but only within the network of
fec0::/10
the organization to which they belong.
In effect, they are the IPv6 equivalent
of the current private network address
space, such as 10.x.x.x.
These are multicast addresses.
ff
A unicast address consists of three basic components:
Public Topology
The rst part (which also contains one of the prexes mentioned above) is used to
route packets through the public Internet. It includes information about the company
or institution that provides the Internet access.
Site Topology
The second part contains routing information about the subnetwork to which to
deliver the packet.
Interface ID
The third part identies the interface to which to deliver the packet. This also allows
for the MAC to form part of the address. Given that the MAC is a globally unique,
xed identier coded into the device by the hardware maker, the conguration
procedure is substantially simplied. In fact, the rst 64 address bits are consoli-
dated to form the EUI-64 token, with the last 48 bits taken from the MAC, and
the remaining 24 bits containing special information about the token type. This also
makes it possible to assign an EUI-64 token to interfaces that do not have a MAC,
such as those based on PPP or ISDN.
On top of this basic structure, IPv6 distinguishes between ve different types of unicast
addresses:
:: (unspecied)
This address is used by the host as its source address when the interface is initialized
for the rst time—when the address cannot yet be determined by other means.
Basic Networking 235