DHCP Tutorial

This tutorial explains the basic concepts of DHCP, how it works and need.

Do I know this Quiz

1.On which port does DHCP servers work on.
2.Name two systems can be configured as DHCP servers
3.Which is the first message a client sends to contact a DHCP server.
4.What is the use of DHCP Offer message.

DHCP Tutorial

What is DHCP

DHCP, which stands for dynamic host configuration protocol is an application layer protocol in the TCP/IP protocol model. It uses UDP at the transport layer and works using a client server architecture.

What is the use of DHCP.

DHCP is used for providing dynamic IP addresses to users on the network. Users on a network require IP addresses for communication. IP address can either be static or dynamic. On a large network, configuring and management of static IP addresses can become cumbersome, due to which the IP addresses are provided dynamically, in which case the appropriate devices are configured as DHCP clients, which receive IP addresses from the DHCP servers on the network.

How does DHCP work

DHCP uses a client server architecture and uses UDP at the transport layer. DHCP clients works on UDP port 68 and servers work on UDP port 67. A DHCP client on a network contacts the DHCP server by initiating a DHCP Discover message, which is a broadcast packet. The message is sent to the destination port of 67 for DHCP servers. When the DHCP server on the network receives the message it responds with a DHCP offer message, which would contain the IP address and other details which the server is willing to offer the client. The client on receipt of the message would respond with a DHCP request message to the DHCP server indicating that it is accepting the parameters. On receipt, the DHCP server responds with a DHCP Ack message, acknowledging the same to the client. It can be observed that 4 messages are exchanged between the client and the server, before which the DHCP client receives the IP address and related parameters.

How to setup a DHCP infrastructure

A DHCP infrastructure contains DHCP clients and servers. TCP/IP adapter of the respective systems have the option to be configured as DHCP clients using the option “obtain IP address automatically”. DHCP servers have to be setup as an additional component. Routers and servers are typical devices which are configured as DHCP servers. These devices would have the service installed on them and can act as DHCP servers. Some examples of systems which can be configured as DHCP servers are Windows 2008, Cisco routers, Linux O/S.

Answers to the Do I know this Quiz

1.DHCP servers work on UDP port 67
2.Linux O/S and Windows 2008 can be configured as DHCP servers
3.DHCP clients send a DHCP Discover message to contact a DHCP server.
4.The DHCP offer message is send by the server to client , which contains the details of IP addresses and other relevant parameters like subnet mask and default gateway which has been allocation to the requested client.