I firstly asked the question here: https://networkengineering.stackexchange.com/questions/33948/restrict-dns-usage-to-some-clients
I would like to create a unbound DNS server. I don't have the IP addresses of the users.
What are some other easy options to consider in order to restrict DNS usage to some clients ?
I am using Openwrt routers behind a nat and my server runs Ubuntu and Unbound as DNS.