router and switch-
1st diffrence-router is a layer 3ree device where switch is 
a layer 2 device
2-router understand ip adrees,where as in the switch in 
understand harwair address.
3=this is the main diffrence which is the best as far as my 
knowledege is conserned
switch break the collison domain and cretae smaller 
collison doman where as router create single brodcast 
domain at each interface,
switch cretae private dedicated collson domain and provide 
independet bandwidth at each port
router and hub-
i have discribed router in first question
now in hub
hub is a also a L2 divice 
hub have the property of
it is multiacess broadcast address
it is multo acess colisson network
it has single colission doman
it has single broadcast doman
hub doecnot create private deidcated collson domain and 
doesnot provide independent bandwith at each port
hub and switch
hub is a
single brodcast domain
single coolision domain
whaer is switch is a multiple coolision doamin and single 
broadcast doman.
switch create private dedicated collison domain and provide 
dedicated bandwith at each interface.ulike hub
bridge and switch
bridge and swith both are L2 device
we can say that switch is a multiport bridge but there are 
some diffrence

(1) bridge use softare to cretae and mange the filter 
table.where as switch uses ASCIS to build and maintan there 
table.bridges can have only one spaing tree whree as switch 
may have many
(2)switches have more number of port then bridges
thanks
jitendera kumar sinha