------- S1-------
en
conf t
spanning-tree vlan 10 priority 4096

------- S2-------
en
conf t
spanning-tree vlan 20 priority 4096

------- S3-------
en
conf t
spanning-tree vlan 30 priority 4096
-------------------------------------------------------------------------

do show span vlan 10
do show span vlan 20
do show span vlan 30

-----------------------------------------------------------------------

in S2 -> do show span | inc Gi0/0