Physical layer device auto-adjustment based on power over Ethernet (PoE) magnetic heating. In one embodiment, information generated by a PoE module that is indicative of the PoE operation over the network cable (e.g., level of current, heating, etc.) is made available to the physical layer device (PHY). This information enables the PHY to infer a change in the level of inductance on the line. In response, the PHY can then adjust a characteristic of transmission by the PHY.