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What Is DHCP?

by Herman Verkade

DHCP is the Dynamic Host Configuration Protocol. It is a network protocol that sends host configuration information to computers (and other devices) on the network. A DHCP server 'leases' an IP address to a client device. When the lease is up, the client needs to renew it, at which point it will receive an update of the configuration information, which makes the client configuration dynamic. Hence, "Dynamic Host Configuration Protocol".

Using DHCP has two major benefits:

1. It can manage your IP address pool. The system administrator gives the DHCP server an range of IP addresses to use. When a client sends a DHCP request, the server will allocate one address from the pool to that client (for the duration of that lease). The server will ensure that each address is leased only once.
2. DHCP can also provide other network configuration parameters to its clients. The network mask and default gateway are required for proper network operation, but it can also be configured to provide the addresses of DNS resolvers, the DNS domain name for the client, the addresses of time servers (NTP), and much more. By using DHCP you can ensure that all devices on the network use the same parameters, and if you need to change one of them, you only need to change it in one place.

DHCP is an internet standard, published as RFC2131. Implementations exist for many different platforms, covering clients and servers. As a standard protocol there is no need to run the same implementation on clients and servers. A Linux client will happily interact with for example a Microsoft DHCP Server, and Windows clients can retrieve their configuration from a Linux system running the DHCP daemon.