3Com S7906E Configuration Manual page 460

An IPv6 address prefix is written in IPv6-address/prefix-length notation, where the IPv6-address is in
any of the notations above mentioned, and prefix-length is a decimal number indicating how many bits
from the left-most of an IPv6 address is the address prefix.
IPv6 address classification
IPv6 addresses fall into three types: unicast address, multicast address, and anycast address.
Unicast address: An identifier for a single interface, similar to an IPv4 unicast address. A packet
sent to a unicast address is delivered to the interface identified by that address.
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.
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 target interface is nearest to the source, according to a routing protocol's measure of
distance).
There are no broadcast addresses in IPv6. Their function is replaced by multicast addresses.
The type of an IPv6 address is designated by the first several bits called format prefix.
mappings between address types and format prefixes.
Table 1-1 Mappings between address types and format prefixes
Type
Unassigned address
Loopback address
Unicast
Link-local address
address
Site-local address
Global unicast
address
Multicast address
Anycast address
Unicast address
There are several types of unicast addresses, including aggregatable global unicast address, link-local
address, and site-local address.
The aggregatable global unicast addresses, equivalent to public IPv4 addresses, are provided for
network service providers. This type of address allows efficient prefix aggregation to restrict the
number of global routing entries.
Format prefix (binary)
00...0 (128 bits)
00...1 (128 bits)
1111111010
1111111011
other forms
11111111
Anycast addresses are taken from unicast address space and
are not syntactically distinguishable from unicast addresses.
1-4
Table 1-1 lists the
IPv6 prefix ID
::/128
::1/128
FE80::/10
FEC0::/10
—
FF00::/8