Embodiments of the invention provide a method for building a classification tree based on a plurality of rules. Each rule includes multiple fields having different priority levels. The classification tree is built to provide for single pass classification of a received packet according to the multiple rules. The classification tree is built level-by-level, where each level represents one of the priority levels. Building a single level of the classification tree includes: creating, for each of the logical decision paths received from a next higher priority level, a respective sub-tree. The sub-tree includes only nodes and related logical decision paths that are necessary to satisfy rules associated with a respective next higher priority level node. Building of the single level further includes: creating, for each non-lowest priority level, logical decision paths from nodes within the current priority level to a next lower priority level.