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The prefix is the part of the address where the bits have fixed values or are the bits of a
route or subnet ident ifier. For example, 21DA:D3::/48 is a route prefix and
21DA:D3:0:2F3B::/64 is a subnet prefix. All subnets have a 64-bit prefix.
Any prefix that
is less than 64 bits is a route or address range that is summarizing a portion of the IPv6
address space.
An
IPv6
prefix
is
useful
only
for
routes
or
address
ranges.
In
IPv4,
it
is
common
to
express an IPv4 address with its prefix length/netmask . For example, 192.168.29.7/24
(equivalent to 192.168.29.7 with the subnet mask 255.255.255.0).
The prefix length is
included so that the bits for identify the subnet and bits for identify the host on the subnet
can be determine. In IPv6 addresses, the number of bits used to identify the subnet is
always
64
and
the
number
of
bits
used
to
identify
the
host
on
the
subnet
is
always
64.
Therefore,
since
the
prefix
length
is
always
64,
sometimes
it
does
need
to
be
expressed.
For example, the address FEC0::2AC4: 2AA:FF:FE9A:82D4/64 can also be represented
as FEC0::2AC4:2AA:FF:FE9A:82D4.
2.4.3.2 IPv6 Address Types
There are three types of IPv6 addresses:
•
Unicast
A
unicast address
identifies
a
single
interface within the scope of the
type of
address. The scope of an address is the region of the IPv6 network over which
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