My new ISP supports IPv6, and I’ve been doing a few tentative tests with it. I actually disabled the DHCPv6 support in my router, and manually configured an address in the ISP-delegated range into my main machine, just for testing. And now I’ve discovered that my other Linux machines have picked up addresses in the delegated range as well, all by themselves! Turns out this is through a mechanism called “SLAAC” (“Stateless Address Autoconfiguration”). My main worry was that, since IPv6 allows direct connections without needing NAT, that internal machines with IPv6 addresses would be directly visible on the Internet. But checking with an external IPv6 ping site seems to show this is not the case: my router is blocking incoming attempts to access nodes on IPv6 addresses by default. The router responds to pings on its own IPv6 address from the public Internet, of course; but other allocated addresses in the range do not respond. Here is a site <https://test-ipv6.com/> I found to test your IPv6 connectivity. It also gives details of the tests it runs, and a handy list of some random places you can access via IPv6.