A method includes a network device receiving a plurality of fragments of an Ethernet frame, where the plurality of fragments include an initial fragment and a first fragment, and where the initial fragment includes a destination media access control (MAC) address field. In response to an error occurring in the Ethernet frame, the first fragment is changed to a second fragment, where the second fragment includes second type indication information (TII) and second to-be-transmitted data (TBTD), where the second TII indicates that a type of the second TBTD is a control character, where a value of first TBTD is different from a value of the second TBTD, and where the second TBTD indicates that an error occurs in the Ethernet frame. The network device sends the second fragment to a destination device.