DHCP

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses and network configuration to devices when they connect to a network. Without it, every device would need a manually configured IP address — which doesn't scale past a handful of devices.

When a device joins a network, it needs four things to communicate: an IP address, a subnet mask, a default gateway, and a DNS server. DHCP provides all of these automatically from a central server — your router, firewall, or a dedicated server — so devices can connect without any manual network configuration.

DORA: how the handshake works

DHCP uses a four-step process called DORA:

Discover — the new device broadcasts a message on the local network (destination 255.255.255.255, source 0.0.0.0) saying "I need an IP address." The client uses UDP port 68; the server listens on UDP port 67.

Offer — the DHCP server responds with an available IP address and lease terms.

Request — the client broadcasts that it's accepting the offered address (this broadcast notifies other DHCP servers their offer wasn't chosen).

Acknowledge — the server confirms, the client configures itself, and it's on the network.

The whole exchange typically completes in under a second.

Static vs dynamic allocation

DHCP doesn't mean every device gets a random address every time. Most DHCP servers support static assignments — binding a specific IP to a device's MAC address so it always gets the same address. This is the right approach for servers, printers, and network devices that need predictable addresses, while still benefiting from centralized IP management rather than manual configuration on each device.