Understanding What Is Dynamic Host Configuration Protocol (DHCP)

In modern hyper-connected IT environments, admins must ensure all the devices are configured correctly and connected in a network. Manually assigning IP addresses to every device is prone to errors. This is where Dynamic Host Configuration Protocol or DHCP configuration comes into play. DHCP is a network management protocol where a server dynamically assigns IP addresses and related information to all the devices on the network for effective communication. Not only IP addresses, but DHCP can also configure a default gateway, subnet mask, Domain Name Server (DNS) and other relevant networking parameters.

DHCP reduces the chances of common errors occurring when IP addresses are assigned manually. It also ensures no two hosts can have the same IP addresses. DHCP plays an important role in managing small networks where mobile devices are used and require IP addresses on a non-permanent basis. The automatic allotment of IP addresses allows mobile devices to move freely from one network to another.

Further, DHCP helps to reduce the typographical errors arising when IP address configuration parameters aren’t defined properly. Since every device must have a unique IP address, duplicate addresses can create conflict where one or both of the devices cannot connect to the network. This happens when addresses are assigned manually. DHCP minimizes the risk of such IP address conflicts. If a change is detected, the DHCP server is updated with new information and the information will be distributed to the new endpoints automatically.

Components of DHCP

DHCP Server

A DHCP server can be a router or a server acting as a host. This is a networked device executing the DHCP service and holding IP addresses and related configuration information.

DHCP Client

A client machine can be a computer, mobile device, or any other device needing to be connected to the network. The client receives configuration information from a DHCP server.

DHCP Relay

DHCP Relay can be a router or a host whose main job is to listen to client messages on the network and then forward them to the server. The server replies by sending responses back to the relay agent passing the message to the client.

IP Address Pool

This is a repository of IP addresses available to DHCP clients. They’re generally assigned sequentially from lowest to highest.

Subnet

IP networks are logically partitioned into two or more segments known as subnets or sub-networks, so they can be managed efficiently.

Lease

The amount of time for which a DHCP client can hold the IP address information.

Working of DHCP

The main role of a DHCP server is to assign unique IP addresses and configure devices automatically. For companies with small networks or at home, a router generally acts as the DHCP server. In large networks, a dedicated server, known as a host, might act as the DHCP server.

The DHCP client device will send a request for the allotment of an IP address to the DHCP Server. This happens when the DHCP client device is switched on and connected to a network. The client sends a DHCPDISCOVER request to the server to communicate over the network.

Once the DHCP server receives the DISCOVER packet, the server offers the client a unique IP address with a DHCPOFFER packet. Once the offer packet reaches the client, it responds by sending a DHCPREQUEST packet to the server to accept it. Once accepted, the server sends an ACK to the client to confirm they’ve been assigned the specific IP address and also to define the amount of time during which the device can use the address before getting a new one. In case the server is unable to assign an IP address to the client, it will send a NACK.

Top Tools for DHCP Configuration Management

There are many paid and free tools out there offering a wide range of solutions for IP address management and are scalable to almost any environment.

SolarWinds IP Address Manager

screenshot of solarwinds ip address manager showing available and used ip addresses

SolarWinds® IP Address Manager (IPAM) is a comprehensive solution providing IP Address Management, DHCP Management, and DNS Monitoring. IPAM is a powerful and scalable solution to help admins automatically manage the allotment of IP addresses and other configuration information. IPAM allows admins to view the details of IP address space usage and IP address conflicts from a single centralized web interface. With this solution, you can manage and monitor the working of Microsoft DHCP servers, Microsoft DNS Servers, and Cisco DHCP servers. It allows users to set DHCP properties, add new or edit existing DHCP servers, and monitor and present DNS information in a consolidated form with DHCP information.

IPAM can also define user roles, grant permissions, and set custom roles. It automatically detects and solves configuration errors. The built-in reports of this tool can extract and represent the data related to IP addresses in a simple and easy-to-understand format. With IPAM, you can periodically scan subnets to avoid IP address conflicts. Companies can deploy IPAM as a stand-alone application or integrate it with SolarWinds Network Performance Monitor for a holistic view of the network. Companies can also opt for a 30-day trial version of IPAM before investing in it.

ManageEngine IP Address Management and Switch Port Mapper

screenshot of manageengine ip address management and switch port mapper's subnet summary report

ManageEngine’s IP Address Management (IPAM) and Switch Port Mapper (SPM) provides an integrated centralized console for switch port mapping and IP address management. With this add-on, information like device type, system name, DNS name, MAC address, state, the name of switch it’s connected to, the port number of the switch it’s connected to, owner, alias name, and other details can be added to IP addresses. Besides, administrators can also add custom fields against each device. IPAM allows admins to find IP address information on a certain day and time with Historical IP Address lookup functionality. With SPM, admins can gain better visibility into each switch port in real time. Companies can take advantage of the benefits of IPAM and SPM add-ons by paying extra.