how dhcp works?

Answer 1

In the context of computer networking, Dynamic Host Configuration Protocol (DHCP, currently implemented as DHCPv6) is a client-server networking protocol. A DHCP server provides configuration parameters specific to the DHCP client host requesting, generally, information required by the client host to participate on an IP network. DHCP also provides a mechanism for allocation of IP addresses to client hosts.

DHCP emerged as a standard protocol in October 1993. RFC 2131 provides the latest (March 1997) DHCP definition. DHCP functionally became a successor to the older BOOTP protocol. Due to the backward-compatibility of DHCP, very few networks continue to use pure BOOTP.

The latest non-standard of the protocol, describing DHCPv6 (DHCP in a IPv6 environment), appeared in July 2003 as RFC 3315.

DHCP stands for Dynamic Host Configuration Protocol. DHCP is capable of supplying each network client with an IP address, subnet mask, default gateway, an IP address for a WINS server and an IP address for a DNS server.

The Dynamic Host Configuration Protocol (DHCP) is a protocol that automates the assignment of IP addresses, subnet masks, default routers, and other IP parameters. The assignment usually occurs when the DHCP configured machine boots up, or regains connectivity to the network. The DHCP client sends out a query requesting a response from a DHCP server on the locally attached network. The DHCP server then replies to the client PC with its assigned IP address, subnet mask, DNS server and default gateway information. The assignment of the IP address usually expires after a predetermined period of time, at which point the DHCP client and server renegotiate a new IP address from the server's predefined pool of addresses. Configuring firewall rules to accommodate access from machines who receive their IP addresses via DHCP is therefore more difficult because the remote IP address will vary from time to time. You'll probably have to allow access for the entire remote DHCP subnet for a particular TCP/UDP port. Most home router/firewalls are configured in the factory to be DHCP servers for your home network. You can also make your Linux box into a DHCP server, once it has a fixed IP address. The most commonly used form of DSL will also assign the outside interface of your router/firewall with a single DHCP provided IP address.

DHCP is a broadcast-based protocol. As with other types of broadcast traffic, it won't cross a router unless specifically configured to do so. If you need such capability, you must configure your routers to pass DHCP traffic that occurs across UDP ports 67 and 68. DHCP operations fall into four basic phases. These phases are IP lease request, IP lease offer, IP lease selection, and IP lease acknowledgement.

IP Lease Request -- Whenever a computer comes on line, it checks to see if it currently has an IP address leased. If it doesn't, it requests a lease from a DHCP server. Because the client computer doesn't know the address of a DHCP server, it uses 0.0.0.0 as its own IP address and 255.255.255.255 as the destination address. Doing so allows the client to broadcast a DHCPDISCOVER message across the network. Such a message consists of the client computer's Media Access Control (MAC) address (the hardware address built into the network card) and its NetBIOS name.

IP Lease Offer -- When a DHCP server receives an IP lease request from a client, it extends an IP lease offer. This is done by reserving an IP address for the client and broadcasting a DHCPOFFER message across the network. This message contains the client's MAC address, followed by the IP address that the server is offering, the subnet mask, the lease duration, and the IP address of the DHCP server making the offer.

IP Lease Selection -- When the client PC receives an IP lease offer, it must tell all the other DHCP servers that it has accepted an offer. To do this, the client broadcasts a DHCPREQUEST message containing the IP address of the server that made the offer. When the other DHCP servers receive this message, they withdraw any offers that they might have made to the client. They then return the address that they had reserved for the client back to the pool of valid addresses that they can offer to another computer. Any number of DHCP servers can respond to an IP lease request, but the client can only accept one offer per network interface card.

IP Lease Acknowledgement -- When the DHCP server receives the DHCPREQUEST message from the client, it initiates the final phase of the configuration process. This acknowledgement phase involves sending a DHCPACK packet to the client. This packet includes the lease duration and any other configuration information that the client might have requested. At this point, the TCP/IP configuration process is complete.
for more information click on the below link:
http://en.wikipedia.org/wiki/DHCP

Answer 2

Consider two computers: a client and a server. The server can be programmed to give any other computers on it's same network an address from a specific range (for example, 192.168.1.2 - 192.168.1.254) If any client tries to connect to the same network, the server will say, "hey, you're not getting on this network unless you allow me to GIVE you an address. You can't make your own address". On clients, there are two options: receive an address automatically and to manually configure one. The client would need to select the option to automatically receive an address. Then the server says, "okay, NOW you're willing to cooperate. I will now give you an address. Welcome to the network".

Answer 3

IT ASSIGN IP ADDRESS AUTOMATICALLY IN NETWORK MACHIN WITH THE HELP OF SOME PROTOCOLS.

Answer 4

This is what you need to read...

http://webmonkey.wired.com/webmonkey/00/39/index3a.html?tw=backend