What Is DHCP?

Dynamic Host Configuration Protocol (DHCP) is a network protocol used to automate the configuration of devices on internet protocol (IP) networks. DHCP is working in our homes and connecting our devices, often without us realizing it. It assigns private IP addresses to our computers, smartphones, Wi-Fi devices, and gadgets, which all use a single network, such as a router, that contains the public IP address. On a wider scope, it connects any device to any IP network, whether it is a local area network (LAN) or a wide area network (WAN).

Devices must connect to a public IP address to send information to each device. As devices use private IP addresses, these do not stay the same and are assigned at each time of use. They collectively dip into a pool of IP addresses that a device uses and put them back when you stop using that device. It would take a long time to configure these manually, so DHCP does this effortlessly, most of the time without us giving it any thought. 

What is the difference between DNS and DHCP?

Domain Name System (DNS) is the service that the internet uses to change domain names like coursera.org into an IP address you can connect to. DHCP, however, is the protocol that automatically gives the devices that connect to a network an IP address. 

Read more: Information Technology (IT) Terms: A to Z Glossary

DHCP components

DHCP consists of three components, the DHCP server, DHCP client, and DHCP relay agents. Let’s take a look at each one and what they are responsible for:

DHCP server configuration

The server issues the IP addresses and can tell the clients on its network apart. The DHCP server allows network administrators to assign rules to clients, such as applying a subnet mask and assigning a remote host to store lease information.

DHCP client

Clients are devices that connect to a network, such as phones, computers, printers, and servers. The communication between the client and server follows a process called the DHCP handshake:

1. Discover: The client who wants to connect to the internet sends a message (packet) to DHCP servers.

2. Offer: The DHCP server receives the message and offers all the available private IP addresses.

3. Request: The client selects an address and sends a message to other clients on the network to make sure the IP address is not already in use.

4. Acknowledge: The DHCP server acknowledges the client’s request and sends all the relevant information needed to connect to the server. 

DHCP relay agents

Relay agents transport the requests between the client and the server. On a small network with limited devices, the relay agent is not necessary, but they are effective in larger networks, especially ones using remote servers.

Related terms

• IT skills

• Computer science

• Help desk technician 

• IT career paths

Get started with DHCP and your IT career on Coursera

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