A broadcast address is a

network address A network address is an identifier for a node or host on a telecommunications network. Network addresses are designed to be unique identifiers across the network, although some networks allow for local, private addresses, or locally administere ...

used to transmit to all devices connected to a multiple-access

communications network A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, message ...

. A message sent to a broadcast address may be received by all network-attached hosts. In contrast, a

multicast address A multicast address is a logical identifier for a group of hosts in a computer network that are available to process datagrams or frames intended to be multicast for a designated network service. Multicast addressing can be used in the link laye ...

is used to address a specific group of devices, and a unicast address is used to address a single device. For

network layer In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers. Functions The network layer provides the means of transfe ...

communications, a broadcast address may be a specific

IP address An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...

. At the

data link layer The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer p ...

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...

networks, it is a specific

MAC address A media access control address (MAC address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. This use is common in most IEEE 802 networking techno ...

IP networking

In Internet Protocol version 4 (

IPv4 Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version de ...

) networks, broadcast addresses are special values in the host-identification part of an

. The all-ones value was established as the standard broadcast address for networks that support broadcast. This method of using the all-ones address was first proposed by R. Gurwitz and R. Hinden in 1982. The later introduction of

subnet A subnetwork or subnet is a logical subdivision of an IP network. Updated by RFC 6918. The practice of dividing a network into two or more networks is called subnetting. Computers that belong to the same subnet are addressed with an identical ...

s and

Classless Inter-Domain Routing Classless Inter-Domain Routing (CIDR ) is a method for allocating IP addresses and for IP routing. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous classful network addressing architecture on the Internet. Its g ...

changed this slightly, so that the all-ones host address of each subnet is that subnet's broadcast address. The broadcast address for any IPv4 host can be obtained by taking the

bit complement In computer programming, a bitwise operation operates on a bit string, a bit array or a Binary numeral system, binary numeral (considered as a bit string) at the level of its individual bits. It is a fast and simple action, basic to the higher-l ...

(bitwise NOT) of the ''subnet mask'' and then performing a

bitwise OR In computer programming, a bitwise operation operates on a bit string, a bit array or a binary numeral (considered as a bit string) at the level of its individual bits. It is a fast and simple action, basic to the higher-level arithmetic operati ...

operation with the host's IP address. A shortcut to this process (for common masks using only 0 and 1 bit placements) is to simply take the host's IP address and set all bits in the ''host identifier'' portion of the address (any bit positions which hold a 0 in the subnet mask) to 1. As shown in the example below, in order to calculate the broadcast address to transmit a packet to an entire IPv4 subnet using the

private IP address In Internet networking, a private network is a computer network that uses a private address space of IP addresses. These addresses are commonly used for local area networks (LANs) in residential, office, and enterprise environments. Both the IP ...

space , which has the subnet mask , the broadcast address is calculated as bitwise ORed with = . A special definition exists for the IP address . It is the broadcast address of the ''zero network'' or , which in Internet Protocol standards stands for ''this network'', i.e. the local network. Transmission to this address is limited by definition, in that it is never forwarded by the routers connecting the local network to other networks. IP broadcasts are used by

BOOTP The Bootstrap Protocol (BOOTP) is a computer networking protocol used in Internet Protocol networks to automatically assign an IP address to network devices from a configuration server. The BOOTP was originally defined in RFC 951. While some part ...

and

DHCP The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a cli ...

clients to find and send requests to their respective servers. Internet Protocol version 6 (

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...

) does not implement this method of broadcast, and therefore does not define broadcast addresses. Instead, IPv6 uses

multicast In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with ...

addressing to the ''all-hosts'' multicast group. No IPv6 protocols are defined to use the all-hosts address, though; instead, they send and receive on particular link-local multicast addresses. This results in higher efficiency because network hosts can filter traffic based on multicast address and do not need to process all broadcasts or all-hosts multicasts.

Ethernet

Broadcast is possible also on the underlying

networks. Frames are addressed to reach every computer on a given LAN segment if they are addressed to

. Ethernet frames that contain IP broadcast packages are usually sent to this address. Ethernet broadcasts are used, among other purposes, by

Address Resolution Protocol The Address Resolution Protocol (ARP) is a communication protocol used for discovering the link layer address, such as a MAC address, associated with a given internet layer address, typically an IPv4 address. This mapping is a critical function ...

to resolve IP addresses to MAC addresses.

IPX networking

Internetwork Packet Exchange Internetwork Packet Exchange (IPX) is the network layer protocol in the IPX/SPX protocol suite. IPX is derived from Xerox Network Systems' IDP. It also has the ability to act as a transport layer protocol. The IPX/SPX protocol suite was very po ...

(IPX) allows broadcast. A packet with ''network number'' of FFFFFFFF is sent to all networks available. When the ''node number'' is specified as FFFFFFFFFFFF, the packet is intended to be received by all hosts in the network.

AppleTalk

The

AppleTalk AppleTalk is a discontinued proprietary suite of networking protocols developed by Apple Computer for their Macintosh computers. AppleTalk includes a number of features that allow local area networks to be connected with no prior setup or the n ...

protocol allows broadcast. When the node ID is specified as 255, a packet is sent to all networks available.

References

{{reflist Network addressing de:Broadcast fr:Broadcast pl:Broadcast

IP networking

Ethernet

IPX networking

AppleTalk

See also

References