IP address

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IPv4 addresses[edit]

IPv4 address, conversion between dotted decimal and binary shown

Internally, IPv4 addresses are represented by a 32bit number. To make it easier to work with them a different notation is used to enter and to display IPv4 addresses. Most commonly IPv4 address are represented by the dotted decimal notation which has the form a.b.c.d, with each letter representing an 8 bit number, with a representing the highest 8 bits of the address and the d the lowest 8 bits. In other words, an IPv4 address is a sequence of four numbers, each between 0 and 255, separated by dots. Examples for valid IPv4 addresses are 127.56.24.12 or 213.239.222.5. By contrast, sequences such as 213.256.222.5 or 127.24.12 or 127.56.24.12.3 are not valid addresses.

Special addresses[edit]

Some address blocks or ranges have been assigned a special meaning.

Reserved address blocks
CIDR address block Range notation Description
127.0.0.1/8 127.255.255.255 Loopback addresses
10.0.0.0/8 10.0.0.0-10.255.255.255 Private network
172.16.0.0/12 172.16.0.0-172.31.255.255 Private network
192.168.0.0/16 192.168.0.0-192.168.255.255 Private network
169.254.0.0/16 192.254.0.0-192.254.255.255 Link-local addresses

IPv6 addresses[edit]

IPv6 address, conversion between hexadecimal and binary shown

Special addresses[edit]

Reserved address blocks
CIDR address block Description
::1/128 Loopback address, localhost
fe80::/10 Link-local addresses
fc00::/7 Unique local addresses
fec0::/10 Site-local addresses (deprecated)
::ffff:0:0/96 IPv4 mapped addresses