On Tue, 11 Sep 2018 at 13:56, Ca By <cb.list6@gmail.com> wrote:

You should provide your users ipv6, opendns supports ipv6 and likely will not have this issue you see

OpenDNS does not support IPv6 for their customisable services "Home" etc. which I believe is the service the OP is using as he refers to the end-user wanting to register their IP address.

Incidentally, I hope OpenDNS considers 100.64.0.0/10 as space that can't be registered to any end-user.

Aled