DNS Rebind Protection¶
You have your dynamic DNS correctly set up, but IPv6 resolving does not work for your domain.
In general DNS Rebinding protection is a safety mechanism to avoid attacks based on DNS-Rebinding. Home routers include a protection mechanism for this attack by never returning a local IP (v4 & v6) address.
In the context of the NextBox this means that, if you are using IPv6, the IPv6 address of your NextBox is considered local by your router and thus wiull not be returned during DNS resolving of your designated domain.
For IPv4 this is also applies, but not a problem. In the IPv4 world (dynamic) DNS resolves to the router (WAN-IP) itself and the router will forward the traffic to your NextBox. In contrast IPv6 will not resolve to your router but to the IPv6 address of your NextBox directly and the router just has to open its firewall for the traffic to pass.
Most routers, which implement this DNS-Rebind protection also allow you to whitelist certain domains from this protection. Generally, to solve this issue you have to insert your (full) domain to the DNS-Rebind Exceptions (or whitelist) of your router.
For instance, the setting inside a Fritz!Box is to be found in: “Home Network -> Network -> Network Settings -> More Settings -> DNS Rebind Protection”. You need to ensure that you have the “extended/expert view” activated.