This attribute provides status information on the port. Valid values include 'disabled'(value 0x00), 'listening' (value 0x01), 'learning' (value 0x02), 'forwarding' (0x03), 'blocking' (value 0x04), 'linkdown' (value 0x05), and 'stp_off' (value 0x06) in accordance with IEEE 802.1D [14]. (Note: The value 'linkdown' is introduced to denote the port status where the Ethernet link state is down. This value is necessary to distinguish the case where Ethernet is physically down and the case where Ethernet is administratively down, which can be denoted by 'disabled.' The value 'stp_off' is introduced to denote the port status where Spanning Tree Protocol is disabled, by setting 'PortSpanningTreeInd' of 'MAC Bridge Port Configuration Data' to FALSE, and Ethernet link state is up. This value is used to distinguish whether or not a bridge port forwarding frames is under control of STP.) Upon autonomous instantiation, the value 0x00 is used.