R1(config)# interface GigabitEthernet 1/0.100
R1(config-subif)# ip nat inside

R1(config-subif)# interface GigabitEthernet 1/0.300
R1(config-subif)# ip nat inside

R1(config-subif)# interface GigabitEthernet 0/0
R1(config-if)# ip nat outside
R1(config-if)# exit