2. Home
  4. Docs
  6. IT and Computer Networkin...
  8. DHCP

DHCP

Print

What is DHCP?

DHCP is one of the types of network management protocols used to assign IP addresses and network configuration to be done automatically (for example, subnet masks, default gateways, DNS servers) to a device in a network. Such configuration will not require much manual configuration, so connecting any device to the network will be much easier. DHCP played an important role for both small- and large-scale network environments, right from home networks to enterprise infrastructures.

How DHCP Works:

  1. DHCP Discovery:
    When a device, also sometimes referred to as a DHCP client, first connects to a network, it literally has no IP address. This is sent as a broadcast DHCP Discovery message in order to locate a DHCP server available in the local network.
  2. DHCP Offer:
    On receiving the discovery message, any DHCP server within the network replies with a DHCP Offer message. This is an offer of an available IP address, subnet mask, default gateway, DNS server addresses, and lease time (which is how long the IP address is going to be assigned to the client).
  3. DHCP Request:
    The client will receive one or more DHCP offers and select one. The client then sends a DHCP Request message back to the server that made the offer, saying that it accepts the offered IP address and network settings.
  4. DHCP Acknowledgment:
    The DHCP server will now respond to the client with a DHCP Acknowledgment message, whereby the IP address lease and the network configuration details are confirmed. The client will now take this information and configure its network interface so that communication can be done on the network.
  5. Lease Renewal:
    The IP address is leased by the DHCP client for some period of time. As the lease expires, the client prepares a DHCP Request to get the lease renewed. In case of approval, the lease period is just prolonged, and the same IP address is allocated to the client.
  6. DHCP Release:
    If the client no longer needs the IP address or it has disconnected from the network, it sends a DHCP Release message to the server. This allows the server to know that the particular IP address is not being used anymore and can subsequently be reallocated.

Key Components of DHCP:

  • DHCP server: A server that dynamically distributes IP addresses and network configuration parameters. There are many such devices, for example, a router, a dedicated DHCP server, or any server functioning through DHCP services.
  • DHCP Client: This identifies any device that requests and is given an IP address by the DHCP server.
  • Lease Time: The lease time over which the IP address is given to a client. The client has to request renewal at the end of the lease because, on the expiration of this lease, the IP address may be reassigned.
  • DHCP Scope: Range of IP addresses that a DHCP server has to issue to clients, like from 192.168.1.100 through 192.168.1.200.
  • Subnet Mask, Gateway, and DNS Servers: Besides an IP address, other pertinent information about the network that the DHCP server can give out includes a subnet mask, default gateway address, and DNS server addresses.

Benefits of DHCP:

  • Automation: Automatically, DHCP assigns IP addresses, thereby reducing the manual configuration in the process and, as a by-product, reducing errors.
  • Flexibility: Adding devices to the network is easily done, and it does not require manual assignment of IP addresses; therefore, dynamic network management becomes easier.
  • Centralized Management: The network administrator is able to manage all the address allocations for IP from one DHCP server, which, in a way, gives him the ability to have ease in the management.

Common Issues with DHCP:

  • IP address conflicts: When the DHCP server has been wrongly configured, an identical IP address can be obtained by two or more devices. There may be a limited IP pool, whereby with a small DHCP scope, the server runs out of its IP addresses, and no more devices could connect.
  • Security Risks: The network is exposed to security threats in the event that DHCP does not secure its operation. Features such as DHCP snooping can eliminate a majority of these security threats.

DHCP in Diverse Environments:

  • Home Networks: Most home networks have the router acting as a DHCP server, which, in turn, takes care of providing IP addresses for all the other devices on the network.
  • Enterprise Networks: DHCP services can be provided through more specialized servers, and advanced functionality such as IP address management (IPAM) and integration with network access authentication systems are typical.

Static IP Addresses vs. DHCP:

Although DHCP is great with its automatic address assignment, there are always those devices, such as servers, printers, or even network infrastructure devices that will need a static IP. These are addresses that must be manually assigned and do not change. Some DHCP servers support IP reservation where certain pieces of hardware always get the same address based on their MAC address.

In conclusion, DHCP is a very important protocol as it makes network management easy and with the automation of address configuration, ensuring devices are able to communicate over the network with no manual configuration. It provides better usability, scalability, and flexibility in both home and enterprise environments.

How can we help?