DHCP Definition

DHCP (dynamic host configuration protocol) is an extensively used TCP/IP (transmission control protocol/Internet protocol) protocol for dynamically assigning IP addresses to devices on a network.

TCP/IP is the suite of communications protocols that forms the basis of the Internet, and thus it is the de facto standard for most types of networks. A protocol is a standardized format for transmitting data between two devices. The TCP/IP suite contains a number of protocols, among the most important of which are TCP and IP.

An IP address is an identifier for a computer, router, printer or other device on a TCP/IP network. Each IP address in the still mainstream IPv4 (Internet protocol version four) standard consists of 32 bits and is written as four sets (also referred to as quads or octets) of three numbers. Each set ranges from zero to 255 and is separated from the other sets by a period, for example and

A dynamically assigned IP address is one that is assigned to a device, account or user as needed rather than in advance. It contrasts with a static IP address, which is one that is semi-permanently assigned to a device, account or user. With dynamic addressing, a computer, user, etc. can have a different IP address every time it connects to the network. In some systems, the device's IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.

DHCP is a client/server protocol. That is, a server (i.e., a specialized computer or program) runs a DHCP program that assigns IP addresses to clients (i.e., computers or other devices) as they log on to the network.

The main advantage of dynamically assigning IP addresses is that it allows such addresses to be reused, thereby greatly increasing the total number of computers and other devices that can use the Internet or other network (which would otherwise be restricted due to the limited number of IP addresses in IPv4). Dynamically assigned IP addresses can also enhance security for individual users because their IP address is different every time they log into the network.

Another important advantage is that it simplifies network administration because the software keeps track of IP addresses and thus relieves the administrator from the very tedious task of having to manually assign a unique IP address to every computer as it enters the network. DHCP is widely employed within organizations, and Internet service providers (ISPs) typically use it to assign IP addresses to dial-up users.

DHCP was introduced as a standard protocol in October 1993. It was adapted by Microsoft for its Windows NT 3.5 operating system in late 1994 and is now a standard feature of most operating systems. For example, DHCP client software is automatically included on all Red Hat Linux 9 installations, and DHCP server software can easily be installed either during installation of the operating system or at a later date.

Created September 9, 2005. Updated December 31, 2005.
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