What is Collision Domain and Broadcast Domain?

Collision is called the error that occurs at the same time both during packet sending and receiving. This is especially the case for devices that operate half-duplex, such as Hub and Repeater, that is, cannot send and receive packets from one port at the same time. Collision Domain is the area where there is a collision. In other words, it is a region where a collision can take place. Since Hubs and Repeaters send the packets they receive to all ports, there is one Collison Domain regardless of how many hubs and devices connected to the hub. Routers and switches have as many ports as there are Collision Domains. Because there is only one packet collision probability on each port. Briefly; While there is one collision domain at the hub, the switches and routers have as many collision domains as each port. Therefore, it is better to use switches and routers instead of hubs in professional networks

Collision Domain Topology in Hubs and Repeaters;

Collision_Domain
Collision_Domain

Collision Domain Diagram in Switches and Routers;

Collision_Domain
Collision_Domain

Broadcast Domain; Devices on the same network broadcast (general broadcasting) in the environment they are in so that they can communicate with other devices found in the network and thus communicate with each other. In this case, there is one Broadcast Domain in each broadcast domain. So, in fact, it can be thought as follows; how many networks there are, there are so many broadcast domains.

If we look briefly here; Since each port of routers has different networks, we can call each port of routers a broadcast domain.

Collision_Domain_6
Collision_Domain

By default, no matter how many switches or hubs are in the environment, the more networks there are, the more Broadcast Domains exist.

Collision_Domain
Collision_Domain

As it creates a virtual port for each VLAN, just like the ports in the switches, since every VLAN will create a network, as a result, there will be a broadcast domain as much as the number of VLANs in the environment.

Collision_Domain
Collision_Domain

Let’s make a summary briefly and make an example;

  • No matter how many ports the Hub is used, there is one Collision Domain in the environment.
  • There are as many ports as Collision Domain in switches and routers.
  • Routers have as many Broadcast Domains as the number of ports.
  • There are as many Broadcast Domains as the number of VLANs.

Let’s give an example of the subject. When we look at the example below, there are 3 broadcast domains in the environment since there are 3 different networks. When we consider that each port of the switches and routers create a collision domain, we see that there are 8 collision domains.

Collision_Domain
Collision_Domain

We tried to briefly and simply explain Collision Domain and Broadcast Domain.

I hope it was a useful article.