DHCP

DHCP(Dynamic Host Configuration Protocol)

We can assign the ip address to the computer by the two ways.They are 

1.     Manual ip configuration(static ip) 

2.     Automatic ip configuration(Dynamic ip) 

• In static ip configuration the ip addresses are assigned manually and they don't change overtime.If we have 5-10 computers then it is easy to assign ip manually to them.

• But if we have a large no.of computers then it is quite difficult to assign the ip address to them.In this situation the IP addresses are assigned easily to the clients by using the DHCP server.

• In DHCP server the IP addresses are automatically assigned to the clients and these IP addresses are known as Dynamic IP addresses  

Communication between client and DHCP server occurs in four steps which is also called DORA(Discovery,Offer,Request,Acknowledgment)

·         Client Broadcast DHCP Packet

In the first step the client computer send a message on the network to find ouyt the DHCP server.This message is called DHCP Discover Message which is broadcasted by client computer.Client broadcast because when a client doesnot know ip address of DHCP server then the only way with the client to communicate and find out the dhcp server 

·         DHCP Server Offer packet to the client 

In this the DHCP will respond to the client discovery message and provides the IP address to the client which is called DHCP offer.

·          DHCP   client send DHCP request message to DHCP server

The client selects the IP address from the DHCP offer message and replies to the server with the DHCP server request.

·         DHCP Ack

In this step DHCP server receives message from client and then checks the availability of the requested ip in pool ,if it still exists available then DHCP server sends an Ack message to the client that it can use the ip address.