DHCP : Dynamic Host Configuration Protocol

Hi Friends,
Let’s support our organizations using simple way of IP Management. DHCP stands for Dynamic Host Configuration Protocol.
Dynamic = Automatic
Host Configuration = Basic Network Configuration
Protocol = Rules which needs to be followed to make this happen.

DHCP is an application which is either installed on Windows Server Operating system or on UNIX OS to service an enterprise in the aspect of IP configuration and management. Its main goal is to provide & configure the client computers with specific ip configuration to enable identification and communication in the network. Prior to DHCP another protocol have been used, it is called BOOTP. BOOTP(Boot Protocol) has only one future that is Reservation. So the administrators who are worked with BOOTP, need to get all the MAC addresses and write them on a notepad to enable the use of BOOTP. After writing all the MAC addresses, the same need to be added to BOOTP table with corresponding IP addresses. That makes lot of work for administrators, even though its an automated process, but admin’s need to work a lot to get the MAC addresses of all the machines in the network. Later it has gained lot of improvements to serve the network and became DHCP.

How to Install and Configure DHCP?
It very simple and straight forward process. First you need to install the application from Add/Remove Windows Components. After installing you will have a console in the Administrative Tools. I think instead of giving lot of steps.. i will post a simple video of 7mins, just watch it for better understanding of this concept.
Video Link
Now you are ready with your DHCP server installed and configured. so lets talk about why and how it is used? As i said previously it is used for Automatic assignment of IP addresses to client computers which are in the same network with DHCP server. This is the way it will be used. Whenever a computer powered on, it will check itself for the network configuration, if it is configured with manual ip address, the machine broadcasts a message that it was powered on. If it is configured to get the ip automatically, then the machine broadcast a message in search of DHCP server. Then starts the process. It is simply called as “DORA” process.
D = Discovery – Request for discovering DHCP server from client machine.
O = Offer – Respective DHCP server Offers the IP Configuration.
R = Received – Client receives the IP configuration.
A = Acknowledgement  - Client Acknowledges that it has received the IP configuration.
Once the client gets the IP configuration, it will then broadcasts another message to all other clients in the network with its identity.
Interview Questions related to DHCP
1. Explain the DORA process
2. What is an exclusion range and reservation?
An exclusion range is a range of IP addresses which needs to be excluded from DHCP scope, so that these IP’s never assigned automatically. A reservation is an IP address will be reserved for a server every time it boots up and it has been done using the MAC address of that server. Before configuring reservations, we need to exclude them from DHCP scope.
3. How do you configure the AD Server, DNS Server, IIS Server and FTP Server using the DHCP server?
Using the reservations only, so that every time the same address will be assigned to the server. If you take a DNS server, it should have same IP all the time, because it is responsible for name resolutions in that network.  If the IP address getting changed every time, its very difficult to the clients which are requesting name resolutions. That is the reason, it should have same IP all the time, we can do that automatically using reservations.
4. What is DHCP relay agent?
DHCP relay agent, is an option configured on DHCP server. Which enables the client machine requests to go through the routers. That means, if the DHCP server is in one network and the client is in another network, these networks are connected by routers. By default the routes will never allow the DHCP packets through them, by configuring this option, these requests will pass between two networks.

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