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What is DHCP?

DHCP, Dynamic Host Configuration Protocol, is a network, communication, and client/server protocol used in IP networks. This feature enables servers to assign computers an electronic IP address from a range of numbers organized for a given network. When a system starts, DHCP assigns different IP addresses, for instance:

1. A computer is turned on by a user with DHCP.
2. The computer requests to send a broadcast (also called DHCPDISCOVER or DISCOVER), for a server to issue a command.
3. The router then directs the packet to the server.
4. The server receives the packet. Based on usage policies and availability unique to the server, it panels the suitable IP address for the client computer on the receiving end. The server then reserves the IP address temporarily, sending it to the customer’s computer on DHCPOFFER or OFFER packet, with that specific IP address info. The server then configures the client’s WINS servers, DNS servers, NTP servers. Moreover, many other services.
5. The client computer then sends DHCPREQUEST packet, to let the server aware of the IP address usage.
6. The server then sends a DHCPACK packet, authorizing the issuance of the IP address and rights to use it for a specific epoch of time.

It means that a client computer is manually configured to use a specific IP address when it uses a static IP address. The biggest error with these static IP addresses is when two different client computers use the same IP address. A conflict results in service denial. The conflict is virtually eradicated with DHCP.

The old IP management protocol has an extension in DHCP, Bootstrap Protocol. This is more beneficial and advanced, and the can handle any requests from BOOTP computers in a segment. However, this system cannot be routed; it is restricted to LAN. If a server administrator is in need of a DHCP server to address various subnets in a LAN, they should configure these relays on the specific routers where these requests pass.

Note that these servers are not secure, as there is no mechanism allowing for authentication between the server and client computers. Both can be deceived; a computer can fake another’s IP address, and attack the server.