The broadcast address for an IPv4 host can be obtained by performing a bitwise OR operation between the bit complement of the subnet mask and the host’s IP address. In other words, take the host’s IP address, and set to ‘1’ any bit positions which hold a ‘0’ in the subnet mask.
Example: For broadcasting a packet to an entire IPv4 subnet using the private IP address space 172.16.0.0/12, which has the subnet mask 255.240.0.0, the broadcast address is 172.16.0.0 | 0.15.255.255 = 172.31.255.255.
255.240.0.0=11111111.11110000.00000000.00000000 172.16.0.0=10101100.00010000.00000000.00000000 10101100.00011111.11111111.11111111=172.31.255.255
Broadcast is possible also on the underlying Data Link Layer in Ethernet networks. Frames are addressed to reach every computer on a given LAN segment if they are addressed to MAC address FF:FF:FF:FF:FF:FF. Ethernet frames that contain IP broadcast packages are usually sent to this address.