A data processing method includes obtaining, by a session management function (SMF) network element from an external network element, a media access control (MAC) address of a terminal device and an Internet Protocol (IP) address corresponding to the MAC address, and sending, by the SMF network element, the MAC address and the IP address to a first user plane function (UPF) network element, where the MAC address and the IP address are used to send an Address Resolution Protocol (ARP) message, and the ARP message includes the MAC address and the IP address.