Several years ago I remember seeing a mathematical justification for it, and I remember thinking at the time it made a lot of sense, but now I can't find it. I think the goal was to make it easier for routers to dump private ranges based on simple binary math, but not sure that concept ever got widely used. Time to start writing out all the binary. -----Original message----- From:Jay R. Ashworth <jra@baylink.com> Sent:Thu 10-05-2017 09:41 am Subject:RFC 1918 network range choices To:North American Network Operators‘ Group <nanog@nanog.org>; Does anyone have a pointer to an *authoritative* source on why 10/8 172.16/12 and 192.168/16 were the ranges chosen to enshrine in the RFC? Came up elsewhere, and I can't find a good citation either. To list or I'll summarize. Cheers, -- jra