!! configure S2

en
conf t
hostname S2

int g1/2
 switchport access vlan 10
exit

!! configure g2/2(vlan 20) & g3/2(vlan 30)

do show vlan bri

int g0/0
 switchport trunk encapsulation dot1q
 switchport mode trunk
exit

do show interface trunk
-----------------------------------------------
!! configure ips to pcs connected to the S2. -> sh ifconfig.sh
!! ping from 1.2 -> 1.4  ||  2.2 -> 2.4   ||   3.2 -> 3.4