DHCP Server

DHCP stands for Dynamic Host Configuration Protocol and is an auto configuration protocol used on IP networks.
Computers that are connected to an IP network must be configured first in order to communicate with each other. There are two different ways of completing this process, either by using the static or dynamic option.
The static option would only be useful in a small network consisting of a couple of hosts. The dynamic option is processed with the help of a DHCP server, which allows a computer to be configured automatically with the important network information that is needed. This option prevents two computers from accidentally being configured with the same IP address, which is very smart.

The DHCP server waits and listens on a local network on UDP port 67, providing clients on the network with a dynamic IP address included with the correct information about the network structure.
Below here is an example of a process where a client retrieves an IP address from a DHCP server while booting.

  1. Client boots up
  2. Clients checks if an DHCP server is available on the network
  3. DHCP server replies and sends its IP address
  4. Client requests for an IP address
  5. DHCP server responds back with an IP address

Below here is an illustration on a network overview consisting of a DHCP server and multiple clients.

dhcp

Before enabling a DHCP service on a server, it is important to consider the network structure such as, subnet, netmask, gateway, range etc.
Below here is an example of a setup for the DHCP service running on a Linux operating system. It is found in the configuration file called “dhcpd.conf”.

subnet 192.168.1.0 netmask 255.255.255.0 {
       range 192.168.1.2 192.168.1.254;
       option routers 192.168.1.1;
       option subnet-mask 255.255.255.0;
       option broadcast-address 192.168.1.255;
       option domain-name-servers 192.168.1.1;
       option domain-name "debianlan";
       default-lease-time 600;
       max-lease-time 7200;
}

References
http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol
http://www.webopedia.com/TERM/D/DHCP.html
http://debianguiden.dk/wiki/DHCP-server

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