DHCP Concept

DHCP stands for Dynamic Host Configuration Protocol. It is used to provide or assign IP v4 addresses to the configure clients within the same network or between two subnets.

                 In window server 2003, DHCP server is not installed by default. Difference between static IP address and dynamic address.

Static IP address                                            Automatic IP address (DHCP)

(1) More time consuming practice.                           (1) Very less time required.

(2) We have to maintain a list.                                  (2) No need, list is maintained by

                                                                                         DHCP.

(3) If wrong information is delivered then                (3) No chance to deliver wrong

     may be communication problem occurred.                 Information.

(4) If same information delivered again then            (4) No chance.

      may be IP address conflict with each other.                                                                     

(5) More overhead on administrator.                        (5) Less overhead on administrator.

(6) If computer is shuffling from network then        (6) In case shuffling, no problem of

      may be communication problem occur.                   Communication.

DHCP Server is used to provide IP address. We can configure DHCP Server by making a scope. In which we can provide lots of information, which is assigned to the client computer.

            A DHCP Server has always Static address. When we configure our client computer obtain IP address automatically then a DORA process communication is performed between DHCP Server and DHCP Client.

(1)   DHCP Discover

When client computer is DHCP enabled then it will start finding DHCP Server by using broadcast communication with the broadcast message packet. The information is attached by client is his NetBios  Name, mac address, s port, d port etc. This message packet is also called Discover Packet.

(2)   DHCP Offer

When a client computer sends broadcast message in the network then DHCP server receives the DHCP Discover Packet and offer IP related information to the requesting client.

(3)   DHCP Request

When DHCP Server offer IP address related information to the requesting client then requesting client request s the DHCP Server for IP address or IP selection request to DHCP Server.

(4)   DHCP Acknowledgement

When DHCP Server receive the request from requesting client for IP address related information then he sends acknowledgement to the requesting client and maintain his record in its database in which IP address, NetBios Name, Lease expire date & time and Mac address which is also called Unique Id.

We can see or view assigned information on client computer by using command prompt with the help of following command: -

C:\>ipconfig/all

  

Scope

Scope has IP related information, which is used to assign to the DHCP client computers dynamically. The information is IP address, exclude the IP from distribution, router IP address, parent domain name (DNS suffix), DNS IP address, WINS IP & Lease etc.

Creating Scope

In one subnet we can create single scope, but in case of multiple subnet we can create two scopes with different subnet. To create the scope, open DHCP Server.

Right click on Server Local then New scope.

A new scope wizard appears on screen.

Scope Sub containers

(i)                 Address Pool

In this sub container, it will contain Start range IP address & End range IP address as specified by the administrator. It will also contain Excluded IP address. You can exclude more IP address or IP address range by right click on this container.

(ii)               Address Leases

In this sub container, it will show the list of assigned IP addresses & NetBios Name of its clients, Lease expiration date & time, Unique Id which is mac address of client computer.

(iii)             Reservation

Reservation is used to ensure that a DHCP client is always assigned the same IP address. We can bound IP address with the client computer by using client computer’s mac address. By using right click on this container, we can reserve IP address for our client computer.

(iv)             Scope options

This sub container offers us to configure more option or skipped options by using scope options. To configure new option right click on this container then configure o

Super Scope

Super scope is a scope, which is used to handle multisubnet scopes. We can configure this Super scope when our DHCP Server is configured to provide IP address between two subnets or we can say when we want to centralized our IP address assignment method between two subnets.

Lease

Lease is a time duration offered by DHCP Server to the requesting client that how long a client computer can use IP address. By default lease duration is 8 days. A client computer can renew its lease after 50% of its lease duration. At the time of renewable request if DHCP Server is not available then the second request sends by the DHCP client at 87.5% of leased duration. We can renew leased duration manually by using following commands: -

To renew the lease duration first of all we have to release the IP address then send the renew request. To release the IP address the command is: -

C:\> ipconfig/release

(To remove configure or lease from DHCP database)

When you execute this command a release message will send to the DHCP Server to release the information from his database. In this process client computer will use 0.0.0.0 as a source address. To renew the leased duration the command is

C:\>ipconfig/renew

A New lease duration is assigned to the client computer by DHCP Server.

Installation of DHCP Server

Go to control panel ->

Then Add/Remove programs ->

Add/Remove windows components then network services ->

Then detail  -> Then DHCP

Check this check box, click ok.

Click Next to install the DHCP.

You can access it from Administrator Tools.

DHCP Domain Environment

If you are going to install DHCP server in Domain environment then we have to authorize the DHCP Server from Active Directory means no other unauthorized DHCP Server will assign IP address to the client computer.

There are two methods to authorized the DHCP Server in Domain Environment

(1)   open DHCP Server console. Right click on server local -> then click Authorize.

It will show you green sign.

(2)   Open DHCP console.

In the left pane, Right click on DHCP icon in the top of the list then manage authorize server.

A new dialog box appears on screen. Click on authorized button.

Type the IP address of DHCP Server. click ok.

It will show you full computer name with IP address of that computer. Click ok.

Again select the IP address from the list to whom you want to authorized and click ok.

DHCP in Workgroup Environment

In case of workgroup environment, DHCP Server computer must be a fresh workgroup computer means it will not be a member of a Domain Controller otherwise it will demand you authorized from Active Directory. But in workgroup environment every computer is independent computer and act as server, so there is no need to authorized from Active Directory.