With the fast development of Internet, the forwarding tables in backbone routers have been growing fast in size. An ideal IP lookup algorithm should achieve constant, yet small, IP lookup time, and on-chip memory usage. However, no prior IP lookup algorithm achieves both requirements at the same time. In this paper, we first propose SAIL, a splitting approach to IP lookup. One splitting is along the dimension of the lookup process, namely finding the prefix length and finding the next hop, and another splitting is along the dimension of prefix length, namely IP lookup on prefixes of length less than or equal to 24 and that longer than 24. Second, we propose a suite of algorithms for IP lookup based on our SAIL framework. Third, we implemented our algorithms on four platforms: CPU, FPGA, GPU, and many-core. We conducted extensive experiments to evaluate our algorithms using real FIBs and real traffic from a major ISP in China. Experimental results show that our SAIL algorithms are much faster than well known IP lookup algorithms.