Attenuation, or the loss of signal strength over distance, is likely the cause of the issue with the 492ft (150m) cable not establishing a link to the switchport. Ethernet standards typically limit the length of copper Ethernet cables to approximately 328ft (100m) for standard performance. Exceeding this distance, as in the case of the 492ft cable, often results in insufficient signal strength to maintain a reliable connection. Options such as cable shielding, incorrect pinout, or near-end crosstalk do not directly relate to the problem described by the excessive cable length.