Utilizing multiple network interfaces when sending data and acknowledgement packages comprises, in a low power and lossy network (LLN) or other network, a sender device comprises two or more network interfaces for communicating with one or more recipient devices. The sender device assesses the transmission capabilities of the network interfaces to determine data rates available for each interface. The sender device specifies which network interface will be used to transfer data and which network interface will be used to receive an acknowledgement from the recipient device. The sender device selects the network interface with the larger data capacity for transmitting a data packet and the network interface with the smaller data capacity for receiving an acknowledgement. The data transmission and the acknowledgement transmission may be transmitted simultaneously. The recipient device uses transmission parameters received from the sender device to determine the data rate with which to transmit the acknowledgement.