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