Dynamic Host Configuration Protocol (dhcp)

Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network.Why is DHCP important?DHCP allows you to manage the networks' IP addresses scopes and other TCP/IP settings like DNS, Default Gateway in the DHCP server.

How does DHCP works?DHCP operates based on the client to server model. DHCP client software sends a DHCP broadcast query requesting the necessary information whenever a computer or a device connects to the network. Any DHCP server on the network may service the request. The DHCP server manages a pool of IP addresses and also informations about client configuration parameters such as default gateway, domain name, the name servers. On receiving a DHCP request, the DHCP server may respond with specific information for each client, as configured by an administrator, or with a specific address and any other information valid for the entire network and for the time period for which the allocation is valid.

A DHCP client typically question for this information immediately after booting, and periodically thereafter before the expiration of the information. A DHCP client will request the same parameter values when an assignment is refreshed. However, the DHCP server may assign a new IP address based on the assignment policies set by administrators.The server must be configured with a scope before a DHCP server can provide clients with IP addresses. The scope of a range of IP addresses can be leased to DHCP clients on a subnet. In addition to IP addresses, a scope can also assign optional parameters to DHCP clients, including the IP address of DNS servers, WINS servers, and routers, and so on. After a scope has been created, it appears within the DHCP tab.

Each DHCP server requires at least one active scope to function on a network. If you have only a few IP addresses, you might need to reserve more IP address for high-priority users.This is why we need exclude IP address to reserve the IP address for higher-priority users while the range outside the excluded IP address will be assign to the normal users.A network administrator reserves a range of IP addresses for DHCP, and each DHCP client on the LAN is configured to request an IP address from the DHCP server during network initialization. This request-and-grant process uses a lease concept with a controllable time period, allowing the DHCP server to reclaim and then reallocate IP addresses that are not renewed.

The DHCP server permanently assigns an IP address to a requesting client from the range defined by the administrator. This is like dynamic allocation, but the DHCP server keeps a table of past IP address assignments, so that it can preferentially assign to a client the same IP address that the client previously had.