CompTIA Network+ N10-007 Certification Exam Notes: What is a Broadcast Domain?

person coding with HTML displayed on 2nd monitorbroadcast domain is a computer network’s logical division, where all nodes could reach each other in the data link layer via broadcast. For instance, let’s say you have multiple computers that are connected to the Layer 2 switch, a device where the network cards of a device stores the physical address or MAC address.

Storing these addresses in the switch would enable it to make a precise decision on how it would direct packets to and from particular devices. You can also configure Layer 2 switches with VLANs for servicing several networks.

As switches know which devices are connected, it likewise knows which network they’re connected to. Learn more about the broadcast domain below so you’ll be prepared for your upcoming CompTIA Network+ N10-007 certification exam.

How a Broadcast Domain Works

From the broadcast domain definition above, you could say that a broadcast is a process that involves the forwarding of packets to all machines in a specific network.

However, only devices that communicate within a given network would obtain broadcast traffic. A broadcast can’t likewise cross network boundaries, so they’re not routable from network to network. Imagine the insane amount of traffic that will need to be generated through various networks and across the Internet if they allowed routing through networks.

server roomA Broadcast Domain at Work

A common example of a broadcast at work is an IP address being assigned dynamically to a specific device through DHCP. The device requesting the IP address will send a broadcast to the network to look for the DHCP server. Once it finds the DHCP server, the server will then forward the requested IP address to the device that requested the address.

The Function of MAC Addresses

A MAC address is a unique address, expressed in hexadecimal value, which is assigned to network interfaces. A Layer 2 switch is responsible for storing this address and knows precisely which port on a switch the address is connected to.

Once a packet with a MAC address is sent to the Layer 2 switch, it will immediately forward it from the connected port to the receiving device. This means that no other devices would need to process the packet, reducing the overall traffic and noise in the network.

In addition, broadcast packets have particular hexadecimal values for the target MAC addresses. When the Layer 2 switch receives this value, it will forward traffic to connected network devices where the broadcast came from. For instance, if your network has 18 devices connected to a switch, all those devices would acquire and process broadcast packets on your network.

In the simplest terms, a broadcast domain is an assembly of devices capable of receiving broadcast traffic from each other. Layer 2 switches are crucial because they store and forward broadcast traffic, and save for where it came from. Broadcast traffic, however, is not that efficient and a significant amount of it could negatively affect network performance. Fortunately, the broadcast process also works to reduce traffic through the use of switches and MAC addresses, allowing for faster and more efficient processes.