A tree data structure for storing strings of searchable data divided into substrings has at least one first type node that has a substring associated with it and at least one second type node that does not having a substring associated with it. A second type node is directly linked to a first type node by a fail transition. A first type node is directly linked to a second type node by a match transition. An IP address lookup system has memory for storing a tree data structure and a controller for storing and loading an incoming IP address. The system has a finite state machine having three stages including a first stage for loading the IP address and performing a length calculation, a second stage for searching the data structure to find a match, and a third stage for determine the next-hop address index.