IPv4 Broadcast Address

A Broadcast Address is an special values in the host-identification part of an IP address.

It is used to sending data multiple recipients at the same time, for example to allow one device to comunicate with all other devices on the network at once.

The device sends its messages to the broadcast address, and the network hardware propagates it to every other device in the group (the broadcast domain).

Calculation

The broadcast address for an IPv4 host is calculated through bitwise OR using the subnet mask and the host IP address.

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.

The IP broadcast address 255.255.255.255 is limited to use for the local (zero / 0.0.0.0) network. Traffic to this address is not forwarded to other networks.