Embodiments of the present invention provide a transmission apparatus, a connection device, and a method, where the apparatus includes N Ethernet Medium Access Control MAC ports, where each Ethernet MAC port is corresponding to a first MII interface, K Ethernet physical layer interfaces, where each Ethernet physical layer interface is corresponding to a second MII interface, and a connection device, where both N and K are positive integers; where the connection device is configured to control a time-division interconnect bus in the connection device or a time-division space-division switching matrix in the connection device to implement a connection between a timeslot of the first MII interface and a timeslot of the second MII interface, where the N Ethernet MAC ports and the K Ethernet physical layer interfaces are separately connected to the connection device by using the first MII interfaces and the second MII interfaces.