Spanning Protocol States

Blocking- frames are not forwarded, but BPDUs are accepted.

Listening: Frames are not forwarded, and the MAC address table is not yet being built. Old, now incorrect MAC table entries are timed out during this state.

Learning: frames are not forwarded, mac addresses table is being built

Forwarding: frames are forwarded and mac address are still being learned.

Disabled - frames are not forwarded, administratively shutdown port.

Only root switches actually originates BPDUs