DHCP (Dynamic Host Configuration Protocol)

DHCP

                  

DHCP (Dynamic Host Configuration Protocol) is a communications protocol that lets network administrators centrally manage and automate the assignment of Internet Protocol (IP) addresses in an organization's network. Using the Internet Protocol, each machine that can connect to the Internet needs a unique IP address, which is assigned when an Internet connection is created for a specific computer. Without DHCP, the IP address must be entered manually at each computer in an organization and a new IP address must be entered each time a computer moves to a new location on the network. DHCP lets a network administrator supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network.

DHCP uses the concept of a "lease" or amount of time that a given IP address will be valid for a computer. The lease time can vary depending on how long a user is likely to require the Internet connection at a particular location. It's especially useful in education and other environments where users change frequently. Using very short leases, DHCP can dynamically reconfigure networks in which there are more computers than there are available IP addresses. The protocol also supports static addresses for computers that need a permanent IP address, such as Web servers.

DHCP is an extension of an earlier network IP management protocol, Bootstrap Protocol (BOOTP). DHCP is a more advanced protocol, but both configuration management protocols are commonly used and DHCP can handle BOOTP client requests. Some organizations use both protocols, but understanding how and when to use them in the same organization is important. Some operating systems, including Windows NT/2000, come with DHCP servers. A DHCP or BOOTP client is a program that is located in (and perhaps downloaded to) each computer so that it can be configured.

Windows 2000 Install DHCP Server

Windows 2000 uses/installs as default TCP/IP protocol. While in a small home network it is easy
to assign manually the IP-addresses (or use the Windows98/ME Auto-IP-configuration and / or
the Windows2000 Auto-IP-configuration), you will on an office network like to use the "comfort"
of using a DHCP-server to control and manage the distribution of IP-addresses.

Like on Windows NT4, where the DHCP-server is only available on NT4-Server and not with
Windows NT4-workstation, the DHCP-server is not included in Windows2000 Professional, but
only on the Windows 2000 Server versions.

Note: on the system, where the DHCP-server is getting installed, you MUST use a static
(= manually assigned) IP-address :

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Like with all other Server related components, you can start the setup of the DHCP-server from
"Configure Your Server", which is part of the "Administrative Tools"

On the left side, expand on "Networking" , select "DHCP" and then start the "Windows Component Wizard" :


To start the "Windows Component Wizard", you could also have used in the Control-Panel the
applet for "Add / Remove Programs" and selected to "Add / Remove Windows Components"


Select (click on) the line "Networking Services" and then click on the button "Details" :

Locate and select the line by placing the checkmark on : "Dynamic Host Configuration
Protocol (DHCP)", (other items may already be selected), continue with "OK"

Back in the window of "Windows Component Wizard", continue now with "Next"

The system will rumble while configuring the network components. and then you are "Finished"

You will need to configure the DHCP-server before.

Windows 2000 Configure DHCP Server

After installing the DHCP-server, you will need to configure it before you can use it:

Select "DHCP" , which is part of the Windows menu "Administrative Tools".

In the left plane, you will see the name and IP-address of the DHCP-server.

  

After installation, a DHCP server is not authorized.
You need to define the range of IP-addresses to be assigned (=distributed) by the DHCP-server.
A definition of a range of IP-addresses (with or without additional options) is called a "Scope":
select your DHCP-server and then either with a right-click or from the menu "Actions" select to
define a "New Scope":

      

Up comes the Wizard

select "Next"

Define a name for your scope

continue with "Next"

    

Define the range of IP-address and the subnet-mask.
Select a range, which does not include the IP-address of the server itself or any other device with a manually  assigned IP-address (like:network printers).

Although you could exclude them in the next step, usually a range is reserved for such manually assigned addresses and then the rest (in this case: 100 - 199 ) is given to the DHCP-server for automatic distribution.

    

If you could not define separate ranges for manually assigned
and DHCP-assigned IP-addresses, then you could here define IP-addresses or ranges of IP-addresses to be excluded: not to be used by the DHCP-server.

Typically, an IP-address is assigned (= "leased" ) for a limited time.
This avoid running out of addresses, when visitors to you office connect to the network and get an IP-address assigned. Without a time-limit, such an IP-address could not be reused.

Usually, 8 days is a good choice and will ensure that people every day in the office will continue to use the same IP-address once assigned to them, since their systems will in time extend the "lease". And if they come back from a 2 week vacation and the "lease" has expired, then the DHCP-server will assign a new IP-address to them.

    

In addition to the IP-address and Sub-Net mask, a DHCP- server can also be use to define other TCP/IP configuration items on the Client systems.

    

If the office network is part of a larger company Wide-Area network (WAN ) then you need to configure the client computers with the IP-address of the Gateway (or Router) to be able to communicate with systems on the WAN.

Enter the IP-address and then click on "Add" to enter the address to the list of Gateways.

    

Are you using a WAN and need to help your clients to locate the IP-addresses of servers (like WebServers) on the WAN ? Or do you intend to have clients connected to the Windows2000 server via the new: "Active Directory" method ?

Then you must configure the clients for use of a DNS-server. Enter the name of your server and the IP-address and click on"Add" to enter the value on the list.

    

You can also configure the WINS server address

    

You need to activate the scope, ( which you can do later with a right-click on the scope and selecting :
"Activate"/"Deactivate" :)

Finished.

You still have to "Authorize" the DHCP-server:
select the server and either right-click or from the menu "Action" select "Authorize" :


Note: on my system, I had to close now the DHCP-windows and open it up again to see, that the DHCP-server is now "Running" :


a quick check on the "Scope Options", which we have configured already:

If required, you can change or add the options of the scope.

You can configure in the "Properties" of the scope, tab : DNS, that once the DHCP-server has assigned an IP-address the address will be updated in the DNS-server, allowing now other systems on the network to locate your system :

Once the DHCP-server is configured and authorized and the scope is activated, IP-addresses will be distributed .

Windows 2000 Display DHCP Server Information

Once the Windows 2000 DHCP-server is installed and configured, you can view the IP-addresses assigned automatically:

Select "DHCP" , which is part of the Windows menu "Administrative Tools". In the left plane, select for the scope to display the "Address Leases":

a quick check on the "Scope Options", which we have configured already:

If required, you can change or add the options of the scope.

A quick look on a Windows95 system, which was configured via the DHCP-server.

           

use "Winipcfg" for Windows95/98/ME or "ipconfig" for Windows NT4 / 2000 to display the configuration values for your network card.
To get all information display, click on the button "More Info >>"