An operation method of a first communication node supporting communications between an Ethernet-based network and a controller area network (CAN) includes: receiving an Ethernet message from a second communication node belonging to the Ethernet-based network; performing an integrity verification on first automotive safety integrity level (ASIL) authentication information included in the Ethernet message; generating a CAN message based on the Ethernet message for which the integrity verification has been completed; and transmitting the CAN message to a third communication node belonging to the CAN.