BOOTP / Bootstrap - The 1993 precursor to DHCP
DHCP provides automatic IP address configuration and other configuration for most devices.
D - Discover - Requesting device sends a DHCP discover packet over broadcast O - Offer - DHCP server sees discover packet and sends an offer over broadcast R - Request - Requesting device picks an IP and sends a request for it over broadcast A - Acknowledgement - DHCP server sends an acknowledgement
In this process, the requesting device uses udp/68 and the DCHP server uses udp/67
Because broadcasts only happen within a subnet, DHCP does not work across subnets. Luckily, we have a way to do this: DHCP Relays
DHCP Relay - Forwards a discover packet to a subnet with a DHCP server
Gem - The subnet mask tells the device which IP address it can communicate with directly and which it needs to send to the local gateway IP.