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1-4
z Multicast address: An identifier for a set of interfaces (typically belonging to different nodes), similar
to an IPv4 multicast address. A packet sent to a multicast address is delivered to all interfaces
identified by that address.
z Anycast address: An identifier for a set of interfaces (typically belonging to different nodes).A
packet sent to an anycast address is delivered to one of the interfaces identified by that address
(the nearest one, according to the routing protocols’ measure of distance).
There are no broadcast addresses in IPv6. Their function is superseded by multicast addresses.
The type of an IPv6 address is designated by the format prefix.
Table 1-1 lists the mapping between
major address types and format prefixes.
Table 1-1 Mapping between address types and format prefixes
Type Format prefix (binary) IPv6 prefix ID
Unassigned address
00...0 (128 bits) ::/128
Loopback address
00...1 (128 bits) ::1/128
Link-local address
1111111010 FE80::/10
Site-local address
1111111011 FEC0::/10
Unicast
address
Global unicast
address
other forms
—
Multicast address
11111111 FF00::/8
Anycast address
Anycast addresses are taken from unicast address space
and are not syntactically distinguishable from unicast
addresses.
Unicast address
There are several forms of unicast address assignment in IPv6, including global unicast address,
link-local address, and site-local address.
z The global unicast address, equivalent to an IPv4 public address, is used for aggregatable links
and provided for network service providers. This type of address allows efficient routing
aggregation to restrict the number of global routing entries.
z The link-local address is used in the neighbor discovery protocol and the stateless
autoconfiguration process. Routers must not forward any packets with link-local source or
destination addresses to other links.
z IPv6 unicast site-local addresses are similar to private IPv4 addresses. Routers must not forward
any packets with site-local source or destination addresses outside of the site (equivalent to a
private network).
z Loopback address: The unicast address 0:0:0:0:0:0:0:1 (represented in shorter format as ::1) is
called the loopback address and may never be assigned to any physical interface. Like the
loopback address in IPv4, it may be used by a node to send an IPv6 packet to itself.