ISL and 802.1q Configuration

Use multiple logical subinterfaces on 1 physical interface that connects the router to the switch.

ISL
interface fastethernet 0.[subinterface]
ip address [address] [subnet]
encapsulation isl [VLAN ID]


802.1q
(note that this uses native vlan, in which no VLAN ID is used on a certain trunk, which by default is VLAN 1)

interface fastethernet 0
ip address [address][subnet mask]

interface fastethernet 0.2
ip address [address][subnet mask]
encapsulation dot1q [VLAN ID]