SW1(config)#spanning-tree vlan 10 root primary
SW2(config)#spanning-tree vlan 20 root primary
SW3(config)#interface fastEthernet 0/1
SW3(config-if)#spanning-tree vlan 20 cost 999
SW3(config-if)#interface fastEthernet 0/2
SW3(config-if)#spanning-tree vlan 10 cost 999

SW1(config)#spanning-tree mode rapid-pvst

SW1(config)#spanning-tree mst configuration
SW1(config-mst)#name Region1
SW1(config-mst)#revision 1
SW1(config-mst)#instance 1 vlan 101-150
SW1(config-mst)#instance 2 vlan 151-200

SW1(config)#spanning-tree mode mst

SW1(config)#spanning-tree mst 1 root primary
SW2(config)#spanning-tree mst 2 root primary

SW3(config)#interface fastEthernet 0/1
SW3(config-if)#spanning-tree mst 2 cost 999
SW3(config-if)#interface fastEthernet 0/2
SW3(config-if)#spanning-tree mst 1 cost 999