It took a while, but I finally got native IPv6 at home from Ziggo, my cable ISP a few months ago. All it took was a new cable modem / home router, because they don't support IPv6 on the one I've had since I signed up with them six years ago. And lo and behold: I got myself some IPv6:
$ ifconfig en0 en0: flags=8863
mtu 1500 ether xx:xx:xx:xx:xx:xx inet6 fe80::8d:5a:e4d:176f%en0 prefixlen 64 secured scopeid 0x8 inet 192.168.78.24 netmask 0xffffff00 broadcast 192.168.78.255 inet6 2001:1c00:d00:7300:xxxx:xxxx:xxxx:xxxx prefixlen 64 autoconf secured inet6 2001:1c00:d00:7300:75bf:1d31:ac76:d080 prefixlen 64 autoconf temporary nd6 options=201 media: autoselect status: active
Although it doesn't say so anywhere on the management interface of the cable modem, it looks like I got a /56 prefix (2001:1c00:d00:7300::/56) from Ziggo.
My understanding is that Ziggo only supports IPv6 with the modem in router mode, so the cable modem acts as a NAT router.
So I wondered: what if I also let my Apple Time Machine act as a router, behind Ziggo's modem/router? I told the Time Machine to configure IPv6 automatically and IPv6 mode native, and this is what happened:
(By the way, does anyone know what "Enable IPv6 Connection Sharing" does? I get the same IPv6 addresses on my computer, it's just that the Airport Utility shows a little less information. In any event, on my Mac I get:
$ ifconfig en0 en0: flags=8863
mtu 1500 ether xx:xx:xx:xx:xx:xx inet6 fe80::8d:5a:e4d:176f%en0 prefixlen 64 secured scopeid 0x8 inet 192.168.78.24 netmask 0xffffff00 broadcast 192.168.78.255 inet6 2001:1c00:d00:73f0:xxxx:xxxx:xxxx:xxxx prefixlen 64 autoconf secured inet6 2001:1c00:d00:73f0:7ccf:266b:8f69:4f46 prefixlen 64 autoconf temporary nd6 options=201 media: autoselect status: active
So either Ziggo / the Ziggo modem delegated a /60 out of the /56 given to the modem. On my regular network, the Time Capsule used the first /64 out of that /60. On the guest network, it uses the second /64:
mtu 1500 options=23 ether xx:xx:xx:xx:xx:xx inet6 fe80::21b:63ff:fe95:7d9b%vlan0 prefixlen 64 scopeid 0x7 inet 172.16.42.23 netmask 0xffffff00 broadcast 172.16.42.255 inet6 2001:1c00:d00:73f1:xxxx:xxff:fexx:xxxx prefixlen 64 autoconf inet6 2001:1c00:d00:73f1:2c25:ea92:9deb:d27f prefixlen 64 autoconf temporary nd6 options=1 vlan: 1003 parent interface: en0 media: autoselect (1000baseT ) status: active
It's a little known fact that Apple's Airport base stations actually run the guest network on VLAN 1003, so if you have multiple Airports (including Time Machines) hooked up to the same wired LAN, the additional base stations can forward packets that arrive over Wi-Fi on the guest network to the base station that acts as the home router.
With both the Ziggo modem and the Apple Time Machine set up as routers with a guest network, that means I have no less than four /64s in use:
Ziggo main network: ...00/64 Ziggo guest network: ...03/64 Time Machine main network: ...f0/64 Time machine guest network: ...f1/64
I also finally ran cat 6 UTP from the living room where the cable modem resides to my home office, so I no longer need to wirelessly extend my network from one end of my apartment to the other, which was neither fast nor reliable, or use the tp-link powerline networking adapters, which are rated for 1200 Mbps but only ran at about 60 Mbps in my setup. They would also hang once a month or so.
Now the only thing I need is some 5 Gbps Ethernet USB dongles.