Overview of DHCP

DHCP is an application layer protocol that automates the configuration process of hosts on a network.

Standard ways that DHCP can operate.

• Dynamic Allocation
  A range of IP addresses is set aside for client devices and one of these IPs is issued to these devices when they request one.
  IP could vary almost everytime it connectsw to the network.

• Automatic Allocation
  A range of IP addresses is set aside for assignment purposes.
  the DHCP server is asked to keep track of which IPs it's assigned to certain devices in the past. Using this information, the DHCP server will assign the same IP to the same machine each time if possible.

• Fixed Allocation
  When a computer requests an IP, the DHCP server looks for its MAC address in a table and assigns the IP that corresponds to that MAC address.

DHCP in Action

DHCP discovery

The process by which a client configured to use DHCP attempts to get network configuration information.

It has four steps.
Server discovery step
All the requests and responds are broadcast

1. DHCP Client requests DHCPSIDCOVER message (from port 68)

2. DHCP Server responds DHPCOFFER message (from port 67)

3. DHCP Client would respond to the DHCOFFER message with a DHCPREQUEST message. -> "Yes, I would like to have an IP that you offered me."

4. DHCP Server responds DHCPACK message.

DHCP lease

All the information that DHCP clients needs to operate in a full fledged manner on the network it's connected to.