Tuesday, October 18, 2011

DHCP Overview

Overview, dynamic host configuration protocol overview, network tutorials, troubleshooting tips, subnetting, IP addressing. DHCP or Dynamic Host Configuration Protocol is a network protocol, which is configured in such a way that is provides the IP addresses to the network computers automatically. There is no need to assign the IP address to the client computers individually. DHCP assigns the IP addresses from the given range of the numbers also called DHCP scope.
On the other end, client computers are configured in such a way that they get the IP addresses automatically from the DHCP server during the boot up process. Additionally, DNS and WINS servers can also be configured with the DHCP server.
When a computer starts up it gets the IP addresses from the DHCP server from the defined pool of addresses.
The assigning of the IP address by the DHCP server can be categorized as follows

1. A user turns on the computer with the DHCP client enabled on it.
2. The client PC sends broadcast request (known as DHCP DISCOVER) and then look for the DHCP server to answer.
3. The DHCP server receives the DISCOVER packet and based on the availability and defined settings, the server choose any available IP address and then give to the client. Then DHCP server sends back to the client with DHCP OFFER with that available address information.

4. Again client sends a request to DHCP server known as DHCP REQUEST, in which it lets the server know that it is using the address offered by the DHCP.
5. The DHCP server then again send a acknowledgement to the client known as DHCP ACK, in which it confirm the client that the specific IP address has been assigned to it for a given period of time.
This process of assigning the IP addresses by the DHCP server also known as DORA (Discover, Offer, Request, and Acknowledgement).
When a computer uses a static IP address there can be the chances of error and conflict when two computers use the same IP address. By using the DHCP server there are no chances of such kind of conflicts and errors.
Along with the IP addresses, the DHCP server also enables the client computers to extract all the settings and configurations from the DHCP server on an IP network. These settings include the Firewall, Router, DNS, NAT, WINS, Gateway and Subnet masks settings.
The overall purpose of the DHCP server is to reduce the workload and error margins, which can occur in assigning the IP addresses manually.
The IP address assigned by the DHCP server is for the limited or leased period of time and if a client needs an to extend that leased period for the IP address then client must send a extension request to the DHCP server before this period expires. If the client do not send an extension request, then this IP address becomes free on expiration and is assigned to another client. If a user wants to change the IP address given by the DHCP server then he/she do it by giving these commands on the command prompt.
“IPconfig/release then IPconfig/renew”.
This command will remove the current IP address and assign a new IP address to the client.
There can also be some reserved addresses based on the MAC address or hostname of the client. These reserved addresses are fixed addresses and can only be assigned to the fixed clients.

How to Setup a DHCP Server?

The installation of the DHCP server in the Windows 2000 or Windows 2003 is quite easy. You can install the DHCP server by using the “Manager Your Server Wizard”.
Open Manager Your Server wizard and select the DHCP server option and press next then you will be asked to enter the name and the description of the DHCP scope.
A scope is a collection of the IP addresses on subnet that use DHCP. In the next window you will be asked to define the range of the IP addresses and the appropriate subnet mask that DHCP server will distribute across the all network. Next you will see a window in which you can add anyIP address, which they don’t want to use because these are already in use for example is an IP address of the company’s router and you don’t want that DHCP server use this address and assign to some other client.
So you can add these addresses in the exclusion field. You can define fix range of the IP addresses for exclusion. In the next step you have to assign the lease duration this means that for how long a client can use the IP address, which it got from the DHCP server. You can assign any lease duration. 10 hours, 1 week, 1 month or 1 year so on.
Next you will be asked to configure the scope of the DHCP options now or you can also configure it later.
Next the DNS and the domain name configurations and settings can be entered. The IP address of the DNS server will be assigned and distributed by the DHCP server.
Next if you have WINS requirements then you can enter the IP address of the WINS server. You can just type the server name into the box and then press resolve it will automatically resolve the name of server and find the IP address.
The next step is to activate the scope in the DHCP server because the DHCP server will not work until and unless you activate the scope. The DHCP server is now installed and you can modify the settings according the structure and the requirements of your network.
Make a plan according to the needs of your network before using the DHCP server.

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