A broadcast domain refers to a logical part of a network, in which any equipment within the network can directly send data to another equipment or device. When in the broadcast domain, data transfer can be done without going through a routing device. Before this can be done, however, the devices are required to share one subnet and the same gateway. They should also be in the same Virtual Local Area Network or VLAN.
Basically, a broadcast domain is reached by sending a frame to the broadcast address of the data link layer. The frame being sent to a specific destination can be detected by all the devices in that location, but only the device to which the frame is addressed will be able to receive it. The interconnections in broadcast domains can only be divided by devices under the layer 3 network, examples of which are layer 3 switches and routers.
There are a few cases wherein broadcast domains need to be restricted. This is done to increase the level of security, and to prevent the devices from receiving unwanted data and from carrying out unauthorized tasks. The restriction of broadcast domains is done by routers. A router has the option to drop some of the broadcast signals it receives. Certain issues are raised regarding this restriction, however, especially in cases where a network requests information from another network via broadcast signals.
The use of the broadcast domain is employed in a number of circumstances. Workstations announcing requests by indicating their location in the network apply the procedures invoking the broadcast domain. Network devices sending data from a single LAN segment to another also make use of the broadcast domain.