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this is my first post, so be gentle with me for sometimes not using the correct terminology.

I am using a Fibre ISP with CG-NAT (DS-Lite). I connect via IPv6 Prefix Delegation with a /56 address space. Since I have no static IP (IPv4) I chose to use an off-site Server to tunnel the ipv4-traffic via tunnel6 to my quasi-static IPv6 home address (ISP does not guarantee a static one but it is now for months).

When checking my WAN address I realized that via ifconfig in my router there was a IPv6 address different from ipv6-test using my laptop, on my mobile a next one (via ipv6-test). And those aren't the link local addresses. The Prefix is of course the same, but the Identifier is different. All of those addresses (pingv6, traceroute6...) end up at my Gateway router.

To my knowledge and a lot of Internet search there should only be 1 WAN public IP. Could someone explain that to me or should I just be happy for multiple WAN IPs.

Thanks alot

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I realized that via ifconfig in my router there was a IPv6 address different from ipv6-test using my laptop, on my mobile a next one (via ipv6-test). And those aren't the link local addresses. The Prefix is of course the same, but the Identifier is different. All of those addresses (pingv6, traceroute6...) end up at my Gateway router.

That's normal. This is why you got a /56 prefix – so that your router could issue individual addresses to each and every device.

To my knowledge and a lot of Internet search there should only be 1 WAN public IP

No, there is no such requirement in IP.

You only see this in IPv4 because the amount of available IPv4 addresses is small and most ISPs can only afford to give one address per residential customer, so your router is forced to issue private addresses and to SNAT all of them to the single WAN address that it has.

But in IPv6, if you have a delegated prefix, then it is completely normal that each device will get its own unique public address from that delegated prefix (indeed this is literally the point of "Prefix Delegation").

Once your devices have global addresses, those addresses can just be directly used on the Internet – there is no need for the router to SNAT them to its own address because they're already global.

And also, this means that "WAN address" in IPv6 is not really the same thing as "public address" anymore. Usually your router has a public WAN address (from SLAAC or DHCPv6-NA) and a public LAN address (from DHCPv6-PD), and your devices also have public LAN addresses issued by your router.

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  • Yes, and it's normal that those addresses are directly assigned to machines in ifconfig, and also normal that they're directly visible to ipv6-test. That's the entire point.
    – u1686_grawity
    Jan 19, 2021 at 8:55
  • Thanks alot for your quick answer! I am aware that every device gets a public unique IPv6 address depending on the Prefix and there is no NATting anymore. But how come that ipv6-test.com/whatismyip.com reveals different WAN IPv6 addresses? On laptop and desktop device they are the same, on mobile different. So laptop and desktop should be different if it is device specific but they show via ipv6-test.com the same address (IPv6).
    – bert
    Jan 19, 2021 at 9:01
  • For the first half, "there is no NATing" literally means "different WAN IPv6 addresses". There's nothing more to it, that's literally the outcome of not having NAT. For the second half, could you clarify what you mean by "the same"? Do you mean that the laptop has the same address as the desktop? Or do you mean that they get the same results from ifconfig versus ipv6-test.com? If it's the former...weird. If it's the latter, note that it is also possible for each device to have multiple addresses from the same prefix (one permanent and several temporary).
    – u1686_grawity
    Jan 19, 2021 at 9:04
  • That cleared things up a little. I thought since I am behind a firewall/gateway I should get via ipv6-test.com the same world-facing address i.e my router-IPv6-address.But when checking the "same" ip-address again I realized that the problem was 2 devices connecting via my local VPN Wireguard server and ipv6-test.com showing the address of that server
    – bert
    Jan 19, 2021 at 19:37

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