Difference Between Hub and Switch

There is a common misunderstanding in these two hardware pieces which are commonly doing the dirty work of networking in almost every network in this artcile i will describe the differnce between these two.

Hubs

 A hub is generally a box with multiple ports. They range from very small to large depending on the requirement. Because hubs can generate a lot of unnecessary network traffic and are

capable of operating only in half-duplex mode (they cannot send and receive

data at the same time), you won’t typically see them used in most modern or

high-density networks (switches are used instead). 

A hub is no more than a repeating device that operates on the physical

layer of the OSI model. It takes packets sent from one port and transmits

(repeats) them to every other port on the device. For example, if a computer

on port 1 of a 4-port hub needs to send data to a computer on port 2, the

hub sends those packets to ports 1, 2, 3, and 4. The clients connected to

ports 3 and 4 examine the destination Media Access Control (MAC) address

field in the Ethernet header of the packet, and they see that the packet is not

for them, so they drop (discard) the packet. Figure 1-5 illustrates an example

in which computer A is transmitting data to computer B. When computer A

sends this data, all computers connected to the hub receive it. Only computer B

actually accepts the data; the other computers discard it.

The best alternatives to hubs in production and high-density networks

are switches, which are full-duplex devices that can send and receive data

synchronously.

Switches

Like a hub, a switch is designed to repeat packets. However, unlike a hub,

rather than broadcasting data to every port, a switch sends data to only the

computer for which the data is intended.

Switches also offer advanced functionality when it comes to handling

transmitted packets. In order to be able to communicate directly with specific

devices, switches must be able to uniquely identify devices based on their MAC

addresses, which means that they must operate on the data link layer of the

OSI model.

Switches store the layer 2 address of every connected device in a CAM

table, which acts as a kind of traffic cop. When a packet is transmitted, the

switch reads the layer 2 header information in the packet and, using the CAM

table as reference, determines to which port(s) to send the packet. Switches

send packets only to specific ports, thus greatly reducing network traffic.

Figure 1-7 illustrates traffic flow through a switch. In this figure, computer

A is sending data to only the intended recipient: computer B. Multiple

conversations can happen on the network at the same time, but information

is communicated directly between the switch and intended recipient, not

between the switch and all connected computers.