configurations field

The configuration field is used in 802.12 training packets instead of the length field known from Ethernet. It corresponds in its length of 2 bytes to the length field, but the configuration information is contained in the first four bits. These are a cascading bit that indicates the configuration of the hub, the promiscuity bit, the bridge bit, and a format bit that indicates whether the end node uses 802.3 or 802.5 packets.