Methods and systems for operating a physical layer device (“PHY”) in an Ethernet network include methods and systems for detecting active link partners and for selecting a mode of operation based on detected active link partners, without user intervention. The PHY monitors fiber link media and copper link media for active link partners. The PHY selects a mode of operation according to detected active link partners. For example, a serial gigabit media independent (“SGMII”) mode of operation is selected when an active copper link partner is detected and an active fiber link partner is not detected. Similarly, a serialize/deserialize (“SerDes”) pass-through mode of operation is selected when an active fiber link partner is detected and an active copper link partner is not detected. The PHY interfaces with the active copper link partner when the SGMII mode of operation is selected. Conversely, the PHY interfaces with the active fiber link partner when the SerDes pass-through mode of operation is selected. The SGMII or SerDes pass-through mode of operation can be prioritized for when active copper and fiber link partners are detected. The prioritized mode can be user selectable or factory set. The invention optionally powers down circuitry associated with an unselected mode of operation.