DHCP definition :

Dynamic Host Configuration Protocol (DHCP)

DHCP एक Network Protocol है जो की सर्वर से connected network computers को एक defined range (Scope) मे automatically IP Address देने के काम मे आती है|

जब एक network का computer start होता है एवं उस कंप्यूटर की DHCP Client service होती है, वो क्लाइंट सर्विस चेक करती है की कंप्यूटर मे static IP address है या computer मे DHCP की setting है| अगर Computer मे DHCP की सेटिंग होती है तो कंप्यूटर DHCP Client service के जरिये DHCP server से IP Address के लिए request करता है| server को जब request मिलती है तो वो उस कंप्यूटर की validity को चेक करने के बाद अपने defined range (scope) and rules के अनुसार एक IP address रिज़र्व करके उस computer को भेज देता है| इस प्रकार उस नेटवर्क computer को IP address मिलता है

What is DHCP?

Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network.

How DHCP assigns IP addresses

DHCP assigns an IP address when a system is started, for example:

1. A user turns on a computer with a DHCP client.
2. The client computer sends a broadcast request (called a DISCOVER or DHCPDISCOVER), looking for a DHCP server to answer.
3. The router directs the DISCOVER packet to the correct DHCP server.
4. The server receives the DISCOVER packet. Based on availability and usage policies set on the server, the server determines an appropriate address (if any) to give to the client. The server then temporarily reserves that address for the client and sends back to the client an OFFER (or DHCPOFFER) packet, with that address information. The server also configures the client's DNS servers, WINS servers, NTP servers, and sometimes other services as well.
5. The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know that it intends to use the address.
6. The server sends an ACK (or DHCPACK) packet, confirming that the client has a been given a lease on the address for a server-specified period of time.

Address lease times

Lease times for all Indiana University campuses are as follows:

• Wired devices: 8 hours
• Wireless devices: 20 minutes
• Stand-alone VoIP phones: 1 week

Static IP addresses

When a computer uses a static IP address, it means that the computer is manually configured to use a specific IP address. One problem with static assignment, which can result from user error or inattention to detail, occurs when two computers are configured with the same IP address. This creates a conflict that results in loss of service. Using DHCP to dynamically assign IP addresses minimizes these conflicts.

More information

For a technical review of DHCP standards, see RFCs 2131 and 2132.

Note:

At Indiana University, UITS prohibits individuals and departments from setting up local DHCP servers on the IU network. Almost all wireless access points, many wired Ethernet routers, and computers running Internet Connection Sharing have built-in DHCP servers. While this makes configuration of a small network easier, it can cause problems when the DHCP servers are used in larger networks. Client computers configured to use DHCP for IP assignment do not need statically assigned IP addresses. In addition, they generally do not need to have addresses configured for DNS servers or WINS servers, as these are also set by the DHCP server. For more, see

What are the DHCP operational policies at IU?