This application provides a method and an apparatus for determining an ethernet MAC address. The method includes: receiving, by a first network device, a first ethernet MAC address from a terminal; and determining, by the first network device, whether the first ethernet MAC address can uniquely identify the terminal or a PDU session of the terminal within a global network range, and sending indication information to the terminal based on a determining result, where the indication information is used to determine a source MAC address of a packet sent by the terminal, and the source MAC address is an ethernet MAC address that can uniquely identify the terminal or the PDU session of the terminal within the global network range.