IANA gives criteria on this subject. For IPv4, Here's what they've got within their "Particular reason handle registry". Meaning, for our applications, anything in these deal with blocks shouldn't be assigned given that they should not be routable "publicly". I think it's a subject of symantics and will get tricky https://meisterp740tom3.bloggazzo.com/35600646/5-simple-techniques-for-255-payday-loan