Broadcast traffic and packets

What is broadcast traffic and packets? Explained with examples

In an operational network, devices generate various types of traffic to communicate with other devices. Broadcast traffic is generated when a network device is unaware of the destination. Broadcast traffic is received by all the devices within the subnet hence it is used to reach all available network devices.

Two examples of broadcast packets are

ARP broadcast packet

DHCP request packet

The following images are showing the destination MAC address for the broadcast packets. One image is for ARP and other one is for DHCP broadcast packets.

Broadcast traffic uses FFFF.FFFF.FFFF as the destination MAC address so it has been sent to all the devices on the network.

dhcp packet

Both packets are showing FFFF.FFFF.FFFF as destination MAC address.

Routers do not forward broadcast packets

The below image show the ARP packet traveling in the network, it reached all the devices in the local area network however ARP packets were not forwarded to another network by the router.

arp broadcast

DHCP also uses broadcast packets. In the below image, you can check how the DHCP server and PC6 are communicating on the network when PC6 received the IP address from the DHCP server.

DHCP packets are received by all the devices on the network. As only PC6 has been configured to receive the dynamic IP, it is the one that is communicating with the server while other PCs are dropping the packets.

Network broadcast

How to check broadcast traffic in the network?

To check the broadcast traffic on the real network, we can use tools like Wireshark to capture the traffic and analyze the packets. On simulation software like packet tracer, we can use inbuilt capturing capabilities to see the type of packets generated and further we can analyze the packets for more details.

Is routing traffic more secure than broadcasting?

Yes, routing the traffic is more secure as the traffic is routed to specific devices and it is more secure as we know about the devices which are receiving the packets while broadcast traffic is sent to all the devices, this is vulnerable when compared to the routed traffic. It poses more threats to the network.

The destination IP address for broadcast

The destination address of the broadcast traffic is

How to reduce broadcast traffic on a network?

To reduce the broadcast traffic on the network, we have to reduce the number of devices in each subnet. More devices means more broadcast traffic as all devices generate some sort of broadcast traffic so instead of having one large network, we can create subnets and use routers to reduce the broadcast traffic.

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