The TCP/IP can send data to all hosts on a local network or to all hosts on all directly connected networks. Such transmissions are called broadcast messages.
For example, the routed routing daemon uses broadcast messages to query and respond to routing queries.
For data to be broadcast to all hosts on all directly connected networks, User Datagram Protocol (UDP) and Internet Protocol (IP) are used to send the data, and the host destination address in the IP header has all bits set to 1. For data to be broadcast to all hosts on a specific network, all the bits in the local address part of the IP address are set to 0. There are no user commands that use the broadcast capability, although such commands, or programs, can be developed.
The broadcast address can be changed temporarily by changing the broadcast parameter in the ifconfig command. Change the broadcast address permanently by using the SMIT fast path smit chinet. Changing the broadcast address may be useful if you need to be compatible with older versions of software that use a different broadcast address; for example, the host IDs are all set to 0.