A “Broadcast Domain” refers to the part of a network that is responsible for the delivery and receipt of data to and from several computers and devices simultaneously. The broadcast domain is used in place of a router to perform the logical requirements of the network or network segment once the devices and computers use the same subnet mask. The broadcast domain therefore directs data effectively using the broadcast address for the specific device or computer.
Broadcast Domain Components
Broadcast domains are interpreted only by layer three devices such as routers and switches (layer 3 compatible) in order to send a frame of data. The broadcast IP address containing only ones is used to send out frames to the computers and devices connected to the network.
A Virtual Local Area Network (VLAN) can be used to create a pseudo or “virtual” broadcast domain via a network where devices and computers would see the network components as a standalone network system. Joining the devices and computers in the VLAN can merge them into a single broadcast domain, including wireless computers and devices.
Broadcast Domain Restriction and Uses
Given the use of the broadcast domain within a network or a network segment, routers and switches attached to networks may refuse or restrict connectivity to broadcast domains. Most routers and switches will ignore or “drop” the signal received from broadcasts, preventing other computers and devices from receiving the data required. In situations where there are more than one networks connected via a switch or router; supposing one network has the capability for automatically assigning IP addresses to the connected devices DHCP, while the other does not. Since DHCP is a broadcast signal, the other network without DHCP will not receive any request from the DHCP-enabled network as the router would ignore or drop the broadcast address request. To correct this problem, a router with customized, Linux-based programming will be able to allow the broadcast to be interpreted and sent out to the other network or networks involved in the transmission of data.
Similarly, the router can be used a security device to prevent the communication between networks. For example, two different networks within an organization may need to share information; however, one department handles issues and other tasks of high sensitivity. If an employee within Network A sends a message out, all computers and devices will receive the Message/Request in Network A. The data will also be sent to the second network via the router or switch connecting the separated networks. At this joint, the router or switch, as aforementioned, may ignore the broadcast thereby isolating or separating the networks from each other. This separation is hailed as an inexpensive method of protecting networks albeit no match for a firewall.
The broadcast domain, in summary, is responsible and necessary in both the joining of different networks and groups of computers or devices, while being able to maintain a level of security and integrity within the network.