What is the IP address "xxx.xxx.xxx.255" reserved for?

The IP address ending in ".255" is typically reserved as a broadcast address for a specific subnet. In Class C networks, the last address in a subnet (where all host bits are set to 1) serves as the broadcast address. This special address allows a network packet to be sent to all devices on that subnet simultaneously, rather than targeting a single device with a unicast address.

For example, in a Class C subnet with a subnet mask of 255.255.255.0, the network ID might be defined as "xxx.xxx.xxx.0", with ".1" to ".254" allocated to individual hosts. Therefore, ".255" is used to reach all hosts within that network.

This functionality is crucial for various network operations, such as ARP requests, service discovery protocols, and certain types of network communications where the sender needs to address all devices without specifying each one individually.