IP address
An IP address is a binary number that uniquely identifies computers and other devices on a TCP/IP network.
An IP address can be private - for use on a
local area network (LAN) - or public - for use on the Internet or other
wide area network (WAN).
IP addresses can be determined statically - assigned to a computer by a
system administrator - or dynamically - assigned by another device on
the network on demand.
IPv4 and IPv6
Internet Protocol (IP) technology was developed in the 1970s to support
some of the first research computer networks. Today, IP has become a
worldwide standard for home and business networking as well. Our
network routers, Web browsers, email programs, instant messaging software - all rely on IP or other
network protocols layered on top of IP.
Two versions of IP technology exist today. Traditional home computer
networks use IP version 4 (IPv4), but some other networks, particularly
those at educational and research institutions, have adopted the next
generation
IP version 6 (IPv6).
IPv4 Addressing Notation
An IPv4 address consists of four
bytes (32 bits). These bytes are also known as
octets.
For readability purposes, humans typically work with IP addresses in a notation called
dotted decimal.
This notation places periods between each of the four numbers (octets)
that comprise an IP address. For example, an IP address that computers
see as
00001010 00000000 00000000 00000001
is written in dotted decimal as
Because each byte contains 8 bits, each octet in an IP address ranges in
value from a minimum of 0 to a maximum of 255. Therefore, the full
range of IP addresses is from
0.0.0.0 through
255.255.255.255. This represents a total of 4,294,967,296 possible IP addresses.
IPv6 Addressing Notation
IP addresses change significantly with IPv6. IPv6 addresses are 16 bytes
(128 bits) long rather than four bytes (32 bits). This larger size
means that IPv6 supports more than
300,000,000,000,000,000,000,000,000,000,000,000,000
possible addresses! As an increasing number of cell phones and other
consumer electronics expand their networking capability and require
their own addresses, the smaller IPv4 address space will eventually run
out and IPv6 become mandatory.
IPv6 addresses are generally written in the following form:
hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh
In this
full notation, pairs of IPv6 bytes are separated by a
colon and each byte in turns is represented as a pair of hexadecimal
numbers, like in the following example:
E3D7:0000:0000:0000:51F4:9BC8:C0A8:6420
As shown above, IPv6 addresses commonly contain many bytes with a zero value.
Shorthand notation
in IPv6 removes these values from the text representation (though the
bytes are still present in the actual network address) as follows:
E3D7::51F4:9BC8:C0A8:6420
Finally, many IPv6 addresses are extensions of IPv4 addresses. In these
cases, the rightmost four bytes of an IPv6 address (the rightmost two
byte pairs) may be rewritten in the IPv4 notation. Converting the above
example to
mixed notation yields
E3D7::51F4:9BC8:192.168.100.32
IPv6 addresses may be written in any of the full, shorthand or mixed notation illustrated above.