You can configure multiple paths with switches to provide fault-tolerance. As you know, having multiple paths means that the network is susceptible to data transmission (bridging) loops. Like bridges, switches can run the spanning tree algorithm to prevent such loops from forming.
By default, the spanning tree protocol is enabled on all Cisco switches. Switch port configuration is automatic when the switch is connected to the network and powered on. Use the following commands to customize the spanning tree protocol.
The following commands disable spanning tree for VLAN 12 and force the switch to be the root of the spanning tree for VLAN 1.
Switch(config)#no spanning-tree vlan 12
Switch(config)#spanning-tree vlan 1 root primary