What is DHCP or Dynamic Host Configuration Protocol?

The Dynamic Host Configuration Protocol, or DHCP, is a protocol for network administration that automates the process of configuring devices on IP networks. This enables the devices to access network services such as DNS and NTP, as well as any communication protocol that is based on UDP or TCP. For devices on a network to be able to connect with devices on other IP networks, a DHCP server will dynamically assign an IP address and other network setup settings to each device on the network. The prior protocol known as BOOTP was improved upon to create DHCP. The Domain Name System (DHCP) is an essential component of the DDI solution (DNS-DHCP-IPAM).

Watch and learn the principles of DHCP from Suzanne in about 20 minutes here.
This video provides a summary of the training that we offer to demystify DHCP, which is part of our DDI introductory course, which also covers DNS and IPAM. If you watch it, you will get knowledge about the function of DHCP, the fundamentals of the DHCP protocol, and the message exchanges that take place between clients and servers.

Also Read: What is IPv6? A general guide all about it

Data on Configuration Transferred by the DHCP Server and Associated Key Values

A requesting client will get configuration data from a DHCP server, which will be based on the policies set by the administrator. This is the fundamental flow. Among the most often requested network settings are the subnet mask, router, domain name server, hostname, and domain name. These parameters are also occasionally referred to as “DHCP Options.”

When the asking client joins the network, it does not yet have an IP address, thus the client broadcasts the request. As a result, the protocol is utilised during the very first stages of the IP communication process. If a dynamic protocol is not used to obtain an IP address, the client is required to make use of a predefined IP address, more commonly referred to as a “static IP address.” This predefined IP address must be manually configured on the client network interface, either through the use of configuration files or a particular command.

The DHCP service provides three important values, which are as follows: 1) There is a reduction in the number of operations that need to be performed: the administrator of the network no longer needs to manually set up each client before the client may access the network. 2) The IP addressing scheme has been optimised, which means that addresses that are no longer needed have been released and are now available to new customers joining. 3) The administrator does not need to manually update a client’s settings whenever that client’s network access point changes. This makes it easier to manage user mobility.

Managing the DHCP Lease Throughout Its Duration

The information about an IP address that was allocated via DHCP is only valid for a predetermined amount of time, which is referred to as a DHCP lease. The length of time for which the lease is valid is referred to as the DHCP lease time. The client will no longer be able to use the IP address once the lease has expired, and he or she will be required to terminate all contact with the IP network unless the client seeks an extension of the lease “rent” through the DHCP lease renewal cycle. Clients will often begin the process of renewing their leases around halfway through the term of the lease to mitigate any negative effects that may result from the DHCP server becoming unavailable at the lease’s expiration. This process of renewal guarantees that IP addresses are reliably assigned to devices. Automatic private internet protocol addressing (APIPA) will be used to pick an address for any device that asks for a new IP version 4 address upon arriving on the network but does not receive a response to its request from the network. These IP addresses are part of the range used by the network.

Usage Scenarios

There are four primary applications of DHCP,: 1. Initial Client Connection: the client makes a request to the DHCP server for an IP address and any other parameter values necessary for accessing the network services 2. 2. IP Usage Extension: The client communicates with the DHCP server to prolong the period that its present IP address is in use. 3. Client Connection After Reboot: The client makes contact with the DHCP server to receive confirmation that it can utilise the same IP address that it was using before the reboot. 4. Disconnection of the client occurs when the client requests the DHCP server to free up its IP address.

DHCP Alternatives

Clients can be automatically provided with information on the network services that they can utilise by using the available DHCP options. Pushing the IP address of the time server, the mail server, the DNS server, and the printer server may be done in an extremely effective manner using this method. This may also be used to supply a file name and a file server that will be utilised by the client to initiate a specific boot process. This is mostly used for IP phones and Wi-Fi access points, but it can also be used for automatically installing clients and servers using PXE (Preboot eXecution Environment).

The DHCP Service Has Been Put Into Implementation

The Internet Systems Consortium provides the DHCP service in its most basic and complete form, making it the organization’s flagship product (ISC). ISC DHCP is a comprehensive open-source solution for constructing DHCP servers, relay agents, and clients. It supports both IPv4 and IPv6, so you may use it with any protocol. The Microsoft DHCP server is among the several items in the DHCP Server category.

DHCP failover is a feature that may be added to the DHCP service to offer high availability and load balancing of traffic. The ISC DHCP Failover requires a primary (master) server in addition to a secondary (backup) server for it to function properly. Both servers must be able to work together. After that, a communication channel that is based on TCP and is referred to as a failover channel has to be established between the two servers.