Switch1(config)#** interface g1/0/20 **
Switch1(config-if)#** switchport trunk encapsulation dot1q **
Switch1(config-if)#** switchport mode trunk **
Switch1(config-if)#** switchport trunk allowed vlan 100,200 **
—
Switch2(config)#** interface g1/0/20 **
Switch2(config-if)#** switchport trunk encapsulation dot1q **
Switch2(config-if)#** switchport mode trunk **
Switch2(config-if)#** switchport trunk allowed vlan 100,200 **