DHCP Server Explained. What is DHCP ?

dhcp server

The Dynamic Host Configuration Protocol in short known as DHCP. It is a protocol applies on TCP/IP networks where a DHCP server dynamically assigns an IP address and other network configuration details like subnet mask, defult gateway to each device on a network. So they can communicate each other and with other IP networked devices as well.

A network device can get IP address in two ways

  • You can manually assign the addresses.
  • The addresses can be assigned automatically.

It is very easy and simple to assign IP address to a networked device . An administrator goes to each of the machines on the network and assigns static IP addresses. But it will be a major problem with this method arises when the network becomes midsized or larger. Think of an administrator trying to individually assign thousands of TCP/IP addresses, subnet masks, default gateways, and all other configuration options needed to run the network to thousands of devices in a network. DHCP server’s task is to centralize the process of IP address allocation and option assignment. You can configure a DHCP server with a range of addresses known as pool. And other configuration information and let it assign all of the IP parameters addresses, default gateways, DNS server addresses.

What is DORA process ?

You must have heard the term DORA process along with DHCP. So what is DORA process then ? The easy way to remember how DHCP works is to know the DORA Process. DORA stands for Discover, Offer, Request, and Acknowledge, and it explains how the DHCP process occurs in step by step. Let’s discuss below.

  1. Discover: At the point when IP networking starts up on a DHCP-enabled client, a special message called a DHCPDISCOVER is broadcasted within the local physical subnet.
  2. Offer: Any DHCP server that hears the request checks its internal database and replies with a message called a DHCPOFFER, which contains an available IP address and other informations. The contents of this message completely depend on how the DHCP server is configured there are numerous options aside from an IP address that you can specify to pass to the client on a Windows Server DHCP server.
  3. Request: The client receives one or more DHCPOFFERs (depending on how many DHCP servers exist on the local subnet), chooses an address from one of the offers, and sends a DHCPREQUEST message to the server to signal acceptance of the DHCPOFFER. This message might also request additional configuration parameters. Other DHCP servers that sent offers take the request message as an acknowledgment that the client didn’t accept their offer.
  4. Acknowledge: When the DHCP server receives the DHCPREQUEST, it marks the IP address as being in use (that is, usually, though it’s not required). Then it sends a DHCPACK to the requested client. The acknowledgment message might contain requested configuration parameters. If the server is unable to accept the DHCPREQUEST for any reason, it forwards a DHCPNAK message to the client. If a client receives a DHCPNAK, it begins the configuration process over again. 5. When the client accepts the IP offer, the address is assigned to the client for a specified period of time, called a lease. After receiving the DHCPACK message, the client performs a final check on the parameters (sometimes it sends an ARP request for the offered IP address) and makes note of the duration of the lease. The client is now configured. If the client detects that the address is already in use, it sends a DHCPDECLINE. In other hand If the DHCP server has given out all of the IP addresses in its pool, it won’t make an offer. If no other servers make an offer, the client’s IP network initialization will fail, and the client will use Automatic Private IP Addressing (APIPA).
Benefits of DHCP

Since DHCP introduced, it has made server administration work easy, few of the benefits of DHCP

  • Reliable IP address configuration: DHCP skips configuration errors caused by manual IP address configuration. Such as typing errors, or address conflicts. It caused when you assign an IP address to more than one networked device at the same time.
  • Reduced network administration: It Centralizes and automates the TCP/IP configuration. The efficient handling of IP address changes for clients that must be updated frequently. Such as those for portable devices that move to different locations on a wireless network. We can define TCP/IP configurations from a central location.

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