Routers

The network  layer (also  called layer3) manages device  addressing  tracks the location  of devices on the network  and determines  the best  way to  move data. Which  means that the network  layer  must transport  traffic  between  devices  that aren't  locally attached. Routers are specified at the  network  layer  and provide  the routing  service switch  an internetwork.

It happens like  this first when a packet is  received  on a  router  interface the destination  IP  address  is checked. If  the packet is not destined for that particular router. It will look  up the  destination network  address  in the  routing table. Once the router chosen  an exit  interface the packet will be sent to that interface to be framed and sent  out on  the local  network. If the router  cannot  find an entry  for the  packets  destination  network  in the  routing  table  the  packets  destination network  in the  routing  table  the router  drops  the packets.