http://www.rfc-editor.org/rfc/rfc6996.txt
RFC 6996: Autonomous System (AS) Reservation for Private Use, J. Mitchell2013-07-01T23:00:00-00:00This document describes the reservation of Autonomous System Numbers (ASNs) that are for Private Use only, known as Private Use ASNs, and provides operational guidance on their use. This document enlarges the total space available for Private Use ASNs by documenting the reservation of a second, larger range and updates RFC 1930 by replacing Section 10 of that document.