1-4
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.
z
Unassigned address: The unicast address :: is called the unassigned address and may not be
assigned to any node. Before acquiring a valid IPv6 address, a node may fill this address in the
source address field of an IPv6 packet, but may not use it as a destination IPv6 address.
Multicast address
Multicast addresses listed in
Table 1-2
are reserved for special purpose.
Table 1-2
Reserved IPv6 multicast addresses
Address
Application
FF01::1
Node-local scope all-nodes multicast address
FF02::1
Link-local scope all-nodes multicast address
FF01::2
Node-local scope all-routers multicast address
FF02::2
Link-local scope all-routers multicast address
