In some embodiments, a system allowing a flexible upgrade of a computer system (e.g. server) to a high-speed network connection comprises base configuration motherboard or network card including a set of low-speed (e.g. 1 Gbps Ethernet) media access controllers (MACs) each connected to a low-speed physical controller (PHY), and a set of high-speed (e.g. 10 Gbps Ethernet) MACs. An expansion card including high-speed PHYs of choice can be connected by an end user to the base configuration motherboard or network card. A flow classifier classifies data sent/received over both high-speed and low-speed ports, and a single driver may control both high- and low-speed ports. One or both of the motherboard and/or expansion card are configured according to a detected type (e.g. physical layer standard, vendor) of expansion card connected to the motherboard and/or type of physical medium connected to the expansion card.