Cisco Catalyst 2960-X Command Reference Manual page 109

Layer 2 Commands
spanning-tree mst root
Examples
This example shows how to configure the switch as the root switch for instance 10:
Switch(config)# spanning-tree mst 10 root primary
Catalyst 2960-X Switch Layer 2 Command Reference, Cisco IOS Release 15.0(2)EX
OL-29043 -01 103