• सुखार्थी त्यजते विद्यं विध्यार्थी त्यजते सुखम्सु sखर्थीन: कुतॊ विद्या कुतॊ विध्यार्थीन: सुखम् ||
  • “Luxury people leave knowledge, but a student leaves Luxury No knowledge for one who seeks Luxury, No luxury for student”
  • न चोर हार्यं न च राज हार्यं न भात्रू भाज्यं न च भारकारि |व्ययं कृते वर्धत एव नित्यं विद्याधनं सर्वधनप्रधानम ||
  • Cannot be snatched away by thief, cannot be snatched away by king, Cannot be divided among brothers, Not heavy either If spent daily, it always keeps growing. The wealth of knowledge is the precious of wealth of all”

Dynamic Host Configuration Protocol







Introduction to DHCP

The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on TCP/IP networks. Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically provides an IP address and other related configuration information such as the subnet mask and default gateway. DHCP allows hosts to obtain necessary TCP/IP configuration information from a DHCP server.

Typically we refer to an application layer protocol as one that provides a service of application to a particular device. It is an application layer protocol that allows a client to dynamically be given an IP address.

 

Application protocols are ones that have transport layer information used to identify the service. In the case of DHCP it is UDP port 67 & 68. 


The DHCP Server (e.g. Windows Server 2003) service provides the following benefits: 


  •  DHCP decreases configuration errors caused by manual IP address configuration, such as typing  errors, or address conflicts due to assignment of an IP address to more than one computer at the same time.                                                                                                                                                                                                                                                                                                                                                                                                                                                         
  • DHCP provides centralized and automated TCP/IP configuration. Administrator is able to define TCP/IP configurations from a central location.                                                                                                                                                                                                                                                                                                                                                                                                                       
  • The efficient handling of IP address changes for portable computers that move to different locations on a wireless network.



DHCP operations

DHCP operations can be summarized in four basic DORA steps

D-    Discover

O-    Offer

R-    Request

A-    Accept

Steps for  assigning IP address usid

DHCP assigns an IP address when a system is booted following steps are followed.:

  1. A user turns on a computer with a DHCP client, the client computer broadcast a request packet called DHCP_DISCOVER,  looking for a DHCP server to reply.
  2. The router forwards the DISCOVER packet to the DHCP server.
  3. The DHCP server receives the DHCP_DISCOVER packet. Based on availability of IP address and usage policies set on the server, the server determines a suitable address to give to the client.
  4. The server then temporarily reserves that address for the client and sends back to the client an  DHCP_OFFER  packet, with that address information.
  5. The client sends a DHCP_REQUEST packet, letting the server know that it expects to use the address.
  6. The server sends an DHCP_PACK packet, confirming that the client has a been given a lease on the address for a server-specified period of time


Steps to configure DHCP across the network using CISCO Packet Tracer

Step 1    Create networks with proper labeling of ports and networks.

Step 2  Configure the ports of routers.Put routing information in the routers.

Step 3 Configure DHCP Server

a.     Static IP address from the range of addresses where we are going to put the DHP.

b.     Put address ranges of  the networks.

Step 4  Configure the ports which are gateway of the networks

a.     Go to command line interface  CLI

                                                              i.      Router> en         (command to enable the router)

                                                            ii.      Router #  conf term        (command for configuring terminal)

                                                          iii.      Router (config)# int  fa0/0  (cmd for interface at which our N/W is attached)

                                                         iv.      Router (config-if)# ip helper-address  192.168.20.2 (IP address of the DHCP Server)

                                                           v.      Router (config-if)#exit

                                                         vi.      Router (config)#exit

                                                       vii.      Router #