Exhaustion of private address space is what actually motivated the beginning of a serious IPv6 effort at a well-known big telco that shall remain anonymous. The

Exhaustion of private address space is what actually motivated the beginning of a serious IPv6 effort at a well-known big telco that shall remain anonymous. The entire private IPv4 address space could have remained amply sufficient, had it not been squandered by excessive subnetting rules. Rearranging was prohibitively expensive - hence moving to IPv6.