The figure shows a router with a switch connected to its FastEthernet 0/1 port and the port has an IPv4 address of 10.0.0.254.  The switch has a computer connected to it and the computer has an IPv4 address of 10.0.0.1.  The computer is testing connectivity to the router, which is the default gateway, by using ping to send an echo request to the router port.  The command used is ping 10.0.0.254.  The router responds with an echo reply.