DHCP v4

Dynamic Host Configuration Protocol (DHCP)

DHCP dynamically allocates an IP address from either a pre configured router or a server. DHCP is managed centrally and saves administration time but if configured incorrectly can lead to devices not being able to connect to the network. When a device is given an IP address the DHCP server also gives out a subnet mask, DNS information and default gateway. DHCP communicates on UDP source port 68 and destination port 67. Below is an image of the process when DHCP is enabled on a client. Discover -> Offer -> Request -> Acknowledge

-During a DHCP discover message a client uses layer 2 and layer 3 broadcast message to find a DHCP server.

-During the offer message a server sends a unicast message to the requesting client.

-During the request message the client returns with a broadcast message to the server requesting an IP address

-Finally the acknowledgement message is a unicast message from the server to client with the IP address.

The key terms within DHCP configurations are; 

• DHCP pool
• Network address 
• Default Gateway
• Subnet Mask 

Here is a simple video of IPv4 DHCP configurations in packet tracer showing the benefits through automation;