ipv6 predated widespread use of nat NAT's RFC was 1994 - although port translation didn't come in until 1996. The same year that IPv6's RFC came in 1996. Had

ipv6 predated widespread use of nat NAT's RFC was 1994 - although port translation didn't come in until 1996. The same year that IPv6's RFC came in 1996. Had ipv6 not been created until say 2010 I suspect it would have looked to be backwards compatible with the widespread use of NAT then.