You have RFC3041 and similar techniques, stateless autoconfig, and a variety of other general things that make it really awful for the default ethernet network size to be something besides a /64. ... I would definitely prefer to see a /56, or maybe a /48, handed out today.
When I first started looking at IPv6, the bottom 64 bits were divided into the bottom 48 bits for a MAC address and 16 more bits that could either be zeros or could be used as a subnet number in roughly Novell Netware style (modulo a local/global bit if you needed one). If you wanted to assign addresses instead of autoconfiguring, that was ok too, but it was obvious how autoconfig would work. It was simple, clean, and flexible, and obviously intended that an ISP would hand most customers a /64, which could easily handle an entire building or medium-complexity campus. Then I ignored those bits for a decade or more, because nobody's IPv6 was much more than experimental. When I came back, I found this ugly EUI-64 thing instead, so not only was autoconfiguration much uglier, but you needed a /56 instead of a /64 if you were going to subnet. Does anybody know why anybody thought it was a good idea to put the extra bits in the middle, or for IPv6 to adopt them? -- ---- Thanks; Bill Note that this isn't my regular email account - It's still experimental so far. And Google probably logs and indexes everything you send it.