Understand the forwarding table or routing table of a router

First, an incoming Layer-2 Frame to a router interface will be de-encapsulated to get the IP Packet inside it.  After that, the router will look at the IP Header to find a field named IP Destination.

Next, it will check that IP destination address with its Routing Table.

       1. If there is a matched, the router will re-encapsulated that packet into a Layer-2 Frame then forward that frame to the matched interface.

       2. If NOT, the router will drop that packet and do nothing.