A method and apparatus for comparing a search key with a plurality of rules of an access control list (ACL) stored in a plurality of content addressable memory (CAM) blocks of a content search system are disclosed. The search key is compared with a plurality of covering prefix entries stored in a covering prefix table, wherein a respective covering prefix entry includes first and second common prefix values. The first common prefix value is shared by all of the rules stored in a first of the CAM blocks, and the second common prefix value is shared by all of the rules stored in a second of the CAM blocks. A bitmap associated with a matching covering prefix entry selectively enables a subset of the CAM blocks for comparison with the search key to determine the highest priority matching rule.