Router

-Router is a Layer -3 device (i.e, works in network layer)
-Main function of a router is routing/ internetworking
-It can be a dedicated hardware router or a software router
-In a production environment we use dedicated hardware routing devices (eg: CISCO, JUNIPER etc.)
-A router does packet switching, i.e, from one interface to another interface of the same router
-It also does packet forwarding
-It performs best path selection
-Considering the CISCO hierarchical model we have different types of routers

• Access layer routers
• Distribution layer routers
• Core layer routers

-A hardware router can be of two types

• Modular router (up-gradable) 
• Fixed router ( not up-gradable)