<< I believe switch and HUB has a diffference. Switch HUB and Router all are different. I understand the difference between a HUB and a router but not Switch and router. >>
If you understand the difference between hubs & routers, the difference between switches & routers should be pretty clear as well.
Switches are just smart hubs - rather than re-broadcasting a packet on all ports it keeps track of systems by MAC addresses & then broadcasts the packet only to the recipient. The end result is essentially the same as a hub, just much more efficient (a hub produces one large collision domain, whereas a switch can direct traffic between two systems without interfering with traffic to & from other systems).
So switches & hubs are essentially the same thing, while routers are the truly different device.
A router is used to share internet access between multiple computers on a network. You might connect a cable modem to the router to share the cable internet. A switch is used to connect multiple computers on a network, though not necessarily using the internet. You could also connect a switch to a router to allow more computers internet access. A switch is like a hub, except "faster".
While that is one application of a router, a more general definition of a router is a device that connects disparate networks.
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