Enabling the spanning tree feature
You must enable the spanning tree feature for the device before any other spanning tree related configurations can take effect. In STP, RSTP, or MSTP mode, make sure the spanning tree feature is enabled globally and on the desired ports. In PVST mode, make sure the spanning tree feature is enabled globally, in the desired VLANs, and on the desired ports.
You can disable the spanning tree feature for certain ports with the undo stp enable command to exclude them from spanning tree calculation and save CPU resources of the device. Make sure no loops occur in the network after you disable the spanning tree feature on these ports.