3. DHCP Broadcast Discovery

When a computer connects to a router, the OS does not know:

• The router’s IP address
• The router’s MAC address

So how does it request an IP?

The Answer: Broadcast

The computer sends a broadcast message on the local network. During the first step of DHCP (Discovery), the computer sends a message to:

IP address: 255.255.255.255
MAC address: FF:FF:FF:FF:FF:FF

This is called a broadcast address
meaning:

All devices on this local network, please listen.

The router (DHCP server) receives this broadcast and replies.