NETWORK DEVICES

Hubs, Switches, Routers and NICs.
HUB: 

Hub is a centralized device provides communication among systems when we have more that 2 computers we need to have a device called hub to interconnect. Disadvantage of a Hub: 

1)When we want to transfer some data from one system to another system.
2)If our network has 24 systems the data packet instead of being sent only to the destined system it is being send to all the network participants. (i.e. 24 systems.)
3)Hubs follow broadcasting
SWITCH:

1)It is an advanced version over a Hub.
2)The main benefit of switch is Unicast. Data packets are transmitted only to the target computer instead of all.
3)Switch maintains a table called MIT (Mac Information Table.) which is generated as soon as we turn on the switch, which acts like an index table and easy the process of finding the networked system. MIT contains the port no, IP address and MAC address.

MAC: (Media Access Control): It is an address burnt in the NIC by the manufacturer.
MAC address is of 48 bits in the farm of Hexa decimal.
Every NIC has its own unique MAC address.
MAC address determines the physical location of a system.
ROUTER:

Router is a device connects two different networks.

Class A network with Class C network etc.

Routing is a process of communication between two different networks.