Some of you might be old enough to know that Cisco IOS supports (or used to support) around 10 different layer-3 protocols (IP being the most popular these days) and each one of them (if it was added to IOS early enough when the parser was still somewhat immature) required its own range of numbered ACL. I’ve summarized all of them in the “IOS Access List numbering scheme” article in the CT3 wiki.
Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.