There are two different connection types for Ethernet communications with the 6K, direct connection and network connection.
Direct connection uses a "cross over" type Ethernet cable. This is similar to a null-modem connection where the receive pair of the 6K ethernet port connects to the transmit pair of the PC's ethernet card and transmit pair of the 6K ethernet port connects to the receive pair of the PC ethernet card. The ethernet card must be capable of 10Mbps transfer.
Network connection requires the use of additional hardware such as a hub, switch, bridge, or router. This scheme uses regular "straight-through" twisted pair cables. All hardware must be capable of 10Mbps transfers. If purchasing a new hub for this connection, make sure that is compatible with this. Many new hubs are designed only for 100Mbps transfers and will not work with the 6K.
Most PC cards are designed for 100Mbps operation but, can also operate at 10Mbps as well.