@mcr314@huitema The original design of stateless autoconfig used the site's network (a /64) and the MAC address of the machine, expanded to 64 bits. That meant that the machine could be tracked across networks, etc., by the low-order 64 bits of the IPv6 address. The purpose of the privacy-preserving addresses was to retain the stateless autoconfig feature (and the consequent ease of administration for small sites), but prevent that sort of tracking.