DHCP - a network Dynamic Host Configuration Protocol, which allows computers to automatically obtain an IP address and other parameters for the network TCP / IP. It is very important for any device, as is the identification of a computer on the network. Without this, such as you can not get online. When working model is used "client-server". That is, the client computer automatically accesses the DHCP server and receives from him he needed parameters for the network. This simplifies the network for normal users, and ultimately reduces the number of errors as it is not necessary to manually set the settings for the computer. DHCP is used in almost all network TCP / IP.

The DHCP protocol has the following methods of IP address allocation:

  1.      Manual distribution. If you use this method of IP address for each computer is set manually, but information about these addresses are stored centrally - server DHCP, that is, if necessary, they are easier to change.
  2.      Automatic distribution. If you use this method, each computer is assigned an arbitrary unused IP address from the range specified by the administrator.
  3.      Dynamic allocation. In this method, each computer is automatically assigned a specific IP address, but not constant, but at a certain time. This is called "leases". After time IP address responds, but you can request a new IP address, which may be the same as what was. A user can also opt out of receiving the address and request a new one.

DHCP Options

In addition to the IP address DHCP can also inform the client computer, and other parameters that he needs to work on the network. This option is DHCP, which include: IP address of the router, subnet mask, DNS servers, domain name DNS.

protocol device

DHCP protocol consists of a DHCP client and server DHCP. Data transmission carried over UDP. The server receives messages from clients on port 67, and sends messages to clients on port 68.

Structure of DHCP messages

All posts of this protocol are divided into fields that contain certain information. All fields are of fixed length. DHCP options field does not have a fixed length.