Before we talk about the differences between these network devices, we have to understand the conflict domain and brocast domain first.
Take bus network topology for example, all the PCs are connecting to the same bus line. If multiple PCs are sending the signal at the same time, it will create a conflict domain on the bus line. So some signals will be weaken or terminated due to the conflict.Just like many cars are sharing the same lane. If they all would like to take the same lane at the same time, for sure, they will run into congestion or even crash each other.
As to brocast domain, it is quite straight-forward. Let‘s say a PC would like to brocast a signal. The signal will be brocast to all the PCs which are connecting to the same network channel.
Hub is a outdated network device which is used for amplify the transmission signal. It does not separate the conflict domain and brocast domain.
Network Bridge could separate the conflict domain but usually it only has two ports and not powerful enough. It was replaced by switch fastly after the switch had been lauched.
Switch could be considered as a multiports network bridge. Typical Layer 2 switch could separate the conflict but not brocast domain.Switch could provide different communication channels for different ports so there will not have conflict domain created. Just like different cars are running on different lanes. They are fast and safe.However, if a PC would like to brocast the signal, whether the destination PCs would like to take it not, as long as they are within the same brocast domain, they will all receive the signals. It is like someone is sending the leaflets on the street, whether you like it or not, he forces you to take it.It wastes a lot resource.
Nowadays, we have a lot of so called Layer 3 switches which could provide routing services as well. In other words, they are routers. And routers can not only separate the conflict domain but also the brocast domain. So if you would like to brocast a message to a group, you could do it with a purpose. Only the target receipients could receive your brocast memssages.
Differences between Hub, Network Bridge, Switch and Router,布布扣,bubuko.com
Differences between Hub, Network Bridge, Switch and Router
原文：http://dongyangping.blog.51cto.com/1299774/1411885