DHCP or Dynamic Host Configuration Protocol is a kind of network management protocol which is generally used on networks having IP/UDP protocols. As the name suggests, the DHCP assigns the IP address and other configuration details to the devices during runtime, i.e, dynamically, so that they can feasibly communicate with other network devices.

When we use DHCP, there is no need for a network administrator as the IP addresses need not be assigned to every device.  Rather, the DHCP server instructs the device to request the IP address and other parameters directly from the ISP (Internet Service Provider). DHCP servers can be deployed in all kinds of the network from a small home network to a large regional network.

Network Protocols are the rules and conventions necessary for effective communication between network devices. They control the exchange of information between the devices and play a very important role in networking.

A brief history of DHCP

When the Reverse Address Resolution Protocol (RARP) was introduced in the year 1984, it was used specifically for devices such as diskless workstations, so that they can obtain IP addresses dynamically. But as RARP used data link layer, its implementation was very difficult on different servers. Bootstrap Protocol (BOOTP) was introduced in the year 1985. DHCP works on this protocol. The concept of a relay agent was introduced in BOOTP which allowed one central server to serve hosts on many IP subnets.

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What does DHCP do?

A connectionless service model is employed by the DHCP network which uses the User Datagram Protocol. When the client broadcasts the message/request, the DHCP operation begins. If the client and the server are not on the same subnet, a Relay Agent is used, so that the two can communicate efficiently. DHCP operates in the following phases:

Server Discovery

DHCP helps the client applications to find the available licenced server on the network automatically so that there is no need for a manual configuration of server information. It allows system administrators to perform their task more efficiently and easily.

IP lease offer

This is the second phase in the DHCP operation. All the senders who have a valid IP address respond with a DHCPOFFER message which holds various information such as details about the client’s hardware, IP address, subnet mask, length of lease and the IP address of DHCP server.

IP lease request

During the IP lease request, the DHCP client responds to the first offer that it receives by broadcasting a DHCPREQUEST message after accepting the offer. The server identification of the server whose offer is accepted is also included in the request message.

IP lease acknowledgement

This is the last phase of the operation of DHCP. The server that issues the accepted offer is asked to broadcast a DHCPACK acknowledgement message to confirm that the transaction is successful. The acknowledgement message contains the IP address and other configuration information. When the acknowledgement is received by the client, the clients bind the TCP/IP protocol to the network adapter so that the communication can take place.

Would you prefer a dynamic allocation of IP addresses over the traditional method? Let us know in the comments section.

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