1. An Internet Protocol address look-up method, the method comprising: inputting a search key into a plurality of routing entries, each one of the respective routing entries having a data string that includes data of a respective prefix and having a mask string that includes length of the respective prefix, each one of the routing entries being included in a ternary content addressable memory (CAM); detecting matching prefixes when the search key matches prefixes from among the prefixes of the routing entries; outputting the mask strings corresponding to the routing entries having the matching prefixes; and comparing lengths of the matching prefixes corresponding to the outputted mask strings to determine a longest prefix matching (LPM) entry, the longest prefix matching entry corresponding to the routing entry having the longest outputted mask string.