http://www.rfc-editor.org/rfc/rfc6598.txt
RFC 6598: IANA-Reserved IPv4 Prefix for Shared Address Space, J. Weil, V. Kuarsingh, C. Donley, C. Liljenstolpe, M. Azinger2012-04-01T23:00:00-00:00This document details the allocation of an additional special-use IPv4 address block and updates RFC 5735. This memo documents an Internet Best Current Practice.