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In this paper, we present a new approach to solve the logical topology reconfiguration problem for IP over WDM networks under dynamic traffic. Based on the measurement of lightpaths' load, a change in the logical topology is made if some lightpath is highly loaded or under utilized. The change can be adding/deleting several lightpaths or just rerouting traffic in the current logical topology. The key idea of our approach is to determine a new logical topology so that the maximum lightpaths' load at the time of reconfiguration is limited by a load-balance indicator, which is pre-defined as a system's parameter. It ensures the network performance (in terms of lightpath utilization) and also increases the lifetime of the logical topology under dynamic traffic changes. Moreover, our approach ensures no network disruption during the reconfiguration process while allowing adding or deleting multiple lightpaths at the same time. The algorithm is formulated as a mixed integer linear programming (MILP). The performance is investigated and compared with Gencata's approach through an illustrative numerical example. Because the proposed MILP is complex and can be applied only to small networks, an approximate model is also presented to solve the problem for some real-size networks.