A network device may include a first forwarding board, a second forwarding board and an interface board. The interface board may include a control apparatus and a network interface chip. The control apparatus may form a first upstream packet flow which is sent to the first forwarding board via a first I/O bus and a second upstream packet flow which is sent to the second forwarding board via a second I/O bus using data packets received through the network interface chip from the exterior of the network device. The control apparatus may selectively connect one of a first downstream packet flow and a second downstream packet flow to the network interface chip through the network interface bus according to an active/standby state of the first forwarding board and the second forwarding board, wherein the first downstream packet flow is processed by the first forwarding board and received through the first I/O bus and the second downstream packet flow is processed by the second forwarding board and received through the second I/O bus.