A method for establishing an Ethernet communication link of a digital protective relay having at least two communication ports, includes: configuring physical layers of a first communication port and a second communication port; determining whether or not auto-negotiation with respect to the first communication port or the second communication port is successful; and replacing configuration information regarding one of physical layers of the first communication port and the second communication port with configuration information regarding the other of the physical layers of the first communication port and the second communication port according to whether or not the auto-negotiation with respect to the first communication port and the second communication port has been successful. Although Ethernet ports of the digital protective relay are connected without priority, the digital protective relay may perform the same operation.