IP address

IP addresses are usually displayed in a human-readable notation, but systems may use them in various different computer number formats.

Such assignments may be on a static (fixed or permanent) or dynamic basis, depending on network practices and software features.

For this purpose, an IP address is recognized as consisting of two parts: the network prefix in the high-order bits and the remaining bits called the rest field, host identifier, or interface identifier (IPv6), used for host numbering within a network.

[1] The subnet mask or CIDR notation determines how the IP address is divided into network and host parts.

In this, the IP address is followed by a slash and the number (in decimal) of bits used for the network part, also called the routing prefix.

IPv4 addresses are usually represented in dot-decimal notation, consisting of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., 192.0.2.1.

[7] In some cases of technical writing,[specify] IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.

In the early stages of development of the Internet Protocol, the network number was always the highest order octet (most significant eight bits).

Depending on the class derived, the network identification was based on octet boundary segments of the entire address.

The class system of the address space was replaced with Classless Inter-Domain Routing (CIDR) in 1993.

However, it was found that this was not always necessary as private networks developed and public address space needed to be conserved.

Computers not connected to the Internet, such as factory machines that communicate only with each other via TCP/IP, need not have globally unique IP addresses.

Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of 192.168.0.0 through 192.168.0.255 (192.168.0.0/24).

The smallest possible individual allocation is a subnet for 264 hosts, which is the square of the size of the entire IPv4 Internet.

All modern desktop and enterprise server operating systems include native support for IPv6, but it is not yet widely deployed in other devices, such as residential networking routers, voice over IP (VoIP) and multimedia equipment, and some networking hardware.

[10] However, the definition of what constituted a site remained unclear and the poorly defined addressing policy created ambiguities for routing.

It avoids the administrative burden of assigning specific static addresses to each device on a network.

It also allows devices to share the limited address space on a network if only some of them are online at a particular time.

Typically, dynamic IP configuration is enabled by default in modern desktop operating systems.

Computers and equipment used for the network infrastructure, such as routers and mail servers, are typically configured with static addressing.

Sticky is an informal term used to describe a dynamically assigned IP address that seldom changes.

Filling the void, Microsoft developed a protocol called Automatic Private IP Addressing (APIPA), whose first public implementation appeared in Windows 98.

[17][18] When IP addresses are assigned by multiple people and systems with differing methods, any of them may be at fault.

In addition, a more limited directed broadcast uses the all-ones host address with the network prefix.

In either case, the sender sends a single datagram from its unicast address to the multicast group address and the intermediary routers take care of making copies and sending them to all interested receivers (those that have joined the corresponding multicast group).

[26][27] In IPv4, anycast addressing is implemented with Border Gateway Protocol using the shortest-path metric to choose destinations.

Anycast methods are useful for global load balancing and are commonly used in distributed DNS systems.

In March 2024, the Supreme Court of Canada decided that IP addresses were protected private information under the Canadian Charter of Rights and Freedoms, with police searches requiring a warrant in order to obtain them.

[34] Computer operating systems provide various diagnostic tools to examine network interfaces and address configuration.

Microsoft Windows provides the command-line interface tools ipconfig[35] and netsh and users of Unix-like systems may use ifconfig, netstat, route, lanstat, fstat, and iproute2 utilities to accomplish the task.