unicast IPv6 address typically consists of a 48-bit global
routing prefix in the most significant portion of the
address, followed by a 16-bit subnet ID and 64 bits
dedicated to the interface identifier. Addresses with
prefixes in the range 2000::/3 to E000::/3 are required
to have 64-bit interface identifiers that follow the EUI-64
format mentioned previously.
Link-local addresses in IPv6 are a new concept compared
to IPv4. These addresses refer only to a particular
physical link and are not forwarded by routers. They are
used only for local communication between devices on
the same physical network segment. Link-local addresses
are part of the link-local prefix FE80::/10 and are
extensively used in IPv6 routing protocols for neighbor
and router discovery, as well as in automatic address
configuration. They are usually dynamically created on
all IPv6 interfaces by adding the 64-bit interface ID to
the FE80::/10 prefix.
IPv6 multicast addresses are part of the FF00::/8 prefix.
There is no broadcast traffic in IPv6, so that functionality
is taken by multicast and anycast traffic in IPv6. There
are several reasons broadcast traffic has been left out of
IPv6, including the fact that each broadcast packet on the
network generates an interrupt on all the devices that are
part of the same broadcast domain, even if the traffic is
not directly meant for them; in addition, broadcast
storms can bring down entire networks. With IPv6, it
was decided to implement the one-to-many type of data
traffic by using multicast. Multicast increases the
efficiency of delivering data from one device to many,
and with IPv6, it gets a larger address space, too. A data
packet sent to a multicast address is delivered to all
interfaces identified by the multicast address. Multicast
addresses also have scope. The scope of a multicast
address can be that of a node, a link, a site, an
organization, or a global scope and is represented by a
scope parameter of 1, 2, 5, 8, or E, respectively. As an