What DHCP is and Types of DHCP Explained

This tutorial explains DHCP and its types in detail. Learn what the DHCP is and what are the advantages and disadvantages of having a DHCP server in the network.

Each device in an IP network requires a valid IP configuration. If the network size is small, an administrator can manually provide an IP configuration to each device. But if the network size is large, assigning and managing the IP configuration on each device can be a challenging task.

For example, suppose you work as a network administrator in a company that has more than 2000 devices in its network. The company bought a new Internet connection and asked you to configure all devices to use the new Internet connection.

Depending on how you previously configured IP configuration on all devices, this task may be an easy or a difficult task for you. If you have previously configured the IP addresses on these devices manually, then you have to manually change the configuration of each device.

However, if you have used DHCP, then you only have to change the configuration on the DHCP server. When the clients either reboot or renew their IP configuration, they will automatically acquire the new IP configuration from the DHCP server.

DHCP gives us a much easier way to manage the network by automatically providing IP configuration to hosts than the classic and tedious method known as static IP addressing where we have to configure IP configuration on each host manually.

No matter whether you have a tiny network or a huge network, DHCP works well in all sizes of networks. You can use DHCP in your home network or can use it in your office or business network.

What is DHCP?

DHCP is a service. It allows devices to acquire their IP configuration dynamically. It is defined in RFC 2131 and 2939. It works in the server/client model. The server offers and delivers IP configurations. Clients request and acquire their IP configurations.

DHCP Address Allocation Methods

To provide an IP configuration, a DHCP server can use three mechanisms. These mechanisms are the following.

dhcp types of methods

Static allocation

In this method, the administrator configures an allocation table on the DHCP server. In this table, the administrator fills the MAC addresses of all clients and assigns an IP configuration to each client.

The DHCP server uses the allocation table to provide IP configurations. When a client requests an IP configuration, the DHCP server checks the table and finds a match. If the DHCP server finds a match, the DHCP server offers the IP configuration that is associated with the MAC address of the client in the match.

Dynamic allocation

In this method, the administrator configures a range of IP addresses on the DHCP server. The DHCP server assigns an IP configuration from the configured range to each client that requests an IP configuration.

In this method, the DHCP offers the IP configuration only for a specific time. This specific time is known as the lease. The IP configuration remains valid until the lease duration is over. Once the lease duration is over, the client is required to obtain a new IP configuration from the server.

Automatic allocation

Same as the dynamic method, in this method, the administrator also configures a range of IP addresses on the DHCP server and the DHCP server assigns an IP configuration from the configured range to each client that requests an IP configuration.

Unlike the dynamic method, in this method, the DHCP server assigns the IP configuration permanently. To assigns an IP configuration permanently, the DHCP server sets the lease duration to infinite. As a result, once the DHCP server chooses an IP configuration from the pool and assigns the IP configuration to a client, the IP configuration remains with that same client indefinitely.

That's all for this introductory part. In the next part of this article, we will understand how DHCP works. If you like this tutorial, please don't forget to share it with friends.

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ComputerNetworkingNotes CCNA Study Guide What DHCP is and Types of DHCP Explained