So, I've been given to believe that IPv6-only clients can access IPv4 servers by using addresses like: ::ffff:0:74.125.226.80 (that would be an address for google.com). I'm not IPv6 yet, but I may be soon. I have a miredo/teredo tunnel set up and I can ping normal IPv6 addresses just fine, but when I run:
ping6 ::ffff:0:74.125.226.80
it fails (Destination unreachable: Address unreachable)
Am I misunderstanding something? Can I actually get to IPv4 hosts over my IPv6 connection?
Answer
::ffff:0:74.125.226.80 is a dotted-decimal address, and not a real IPv6 address.
If you only have full, world-routable IPv6 address (with prefix and a /48) then you cannot communicate with the IPv4 world without a special tunnel.
They are for all intents and purposes two different protocols. You have two choices for communication between the two:
Dual-stack. Have both IPv4 (behind a NAT if need be) AND IPv6 (with a world-routable IP, and a link-local address) installed and configured. OS's will try to use IPv6 first, and fall back to IPv4 if that fails. Just make sure you're configured correctly (not a dotted-decimal address like above) and it works pretty seamlessly.
Tunnelling. If you have an IPv6 device, it needs to be aware of an IPv4 tunnel that it can use to broker your connections to the IPv4 world.
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