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Power consumption has become a limiting factor in designing next generation network routers. Recent observation shows that IP lookup engines dominate the power consumption of core routers. Previous work on reducing power consumption of routers mainly focused on network- and system-level optimizations. This paper represents the first thorough study on the data structure optimization for lowering the power consumption in static random access memory (SRAM)-based IP lookup engines. Three different SRAM-based IP lookup architectures are discussed: nonpipelined, simple pipelined, and memory-balanced pipelined architectures. For each architecture, we formulate the problem of power minimization by revisiting the time-space tradeoff in multibit tries. Two distinct multibit trie algorithms are investigated: the expanded trie and the tree bitmap trie, which are widely used in SRAM-based IP lookup solutions. A theoretical framework is proposed to determine the optimal strides for building a multibit trie so that the worst-case power consumption of the IP lookup architecture is minimized. Experiments using real-life routing tables including both IPv4 and IPv6 data sets demonstrate that careful selection of strides in building the multibit tries can reduce the power consumption dramatically. We believe our methodology can be applied to other variants of multibit tries and can help in designing more power-efficient SRAM-based IP lookup architectures.