Mobility support in future internet is quite important because mobile computing and mobile browsing are getting more widespread. In order to reduce the routing overhead, IPv6 allows the mobile node to send the binding updates to any correspondent node so that the correspondent node can send packets to the mobile node directly (also named as the route optimization). And it is obvious that the procedure of binding update will become complex for the movement of a network. Because several active connections may exist within a moving network and each of them may have different correspondent nodes. In this paper, the two-tier concept is proposed so that the binding update procedures of the mobile node can be the same no matter when it travels alone or travels with a mobile network. And the multicast based binding update scheme is proposed for mobile networks (MONET). The simulation results illustrate that the proposed scheme can effectively reduce the number of binding update messages especially when the number of nodes in the mobile network is large and the percentage of directly transmitted packets can also be improved.