Follow these directions to routing table on a Cisco router or switch in IOS.
Here is a simplified example routing table.
Gateway of last resort is 0.0.0.0 to network 0.0.0.0 D 0.0.0.0/0 [1/2] via 192.168.0.1, 1424:17:58, C 127.0.0.0/8 is directly connected, GigabitEthernet0/0 192.168.0.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.0.0/24 is directly connected, GigabitEthernet0/0L 192.168.0.1/24 is directly connected, GigabitEthernet0/0
Notice GigabitEthernet0/0. GigabithEthernet0/0 connects to the switch and the LAN.
When the router receives a packet with destination IP address 192.168.x.x, the packet is sent out the GigabithEthernet0/0 interface (to the switch). When the router receives a packet where the destination IP address is not 192.168.x.x, the Gateway of last resort is used, which is Serial 0/0/0 which connects to the ISP.