VLAN means virtual local area network.Vlans are used to separate multiple
networks while being on the same physical network.
View existing Vlans :
router(config)#show vlan
Configuring a Vlan:
router(config) #configure terminal
router(config)#vlan
router(config)#interface range gigabitEthernet 1/0/2-6
router(config)#switchport access vlan