A method and system establish a bi-directional tunnel through direct communication between a tunnel end point (TEP) and a user node without user assistance. The method includes: operating the user node in order to establish the bi-directional tunnel, wherein operating the user node includes: requesting network information necessary for establishing the bi-directional tunnel to the DHCP server; when the user node receives the network information from the DHCP server, establishing a unidirectional tunnel from the user node to the TEP based on the received network information; requesting one of the TEPs to establish the unidirectional tunnel; and when the user node receives a router advertisement (RA) message of a second network with which the user node wishes to communicate from the TEP required to establish the unidirectional tunnel, establishing an address of the user node in the second network.