I have read Can I create a DC without a DNS Server?. But my question is a bit different.
I have one client in a completely different subnet from the DC. That client does not have access to the appropiate DNS structure for the domain, but can otherwise connect to the DC. I would like to tell that client "the DC for domain example.net is at dc1.site2.example.com". I have seen, that this sort of thing is possible for kerberos things using ksetup /addkdc. Is there something like this for generic AD?
Split horizon, or dual DNS zones still leaves a large amount of ambiguity. If you have Microsoft DNS servers on both sides, each hosting their own AD (or one side hosting AD, and the remote branch with a Windows DNS server), you can specify conditional DNS forwarders in the remote branch DNS server. It will forward all requests (A, AAAA, SRV, PTR, etc.) for said domain example.net to DNS server at specified IP.
Think of conditional forwarders as "overrides" for DNS domains.
From this video, think of the 192.168.2.2 DNS server as your remote site DNS server, and the ISP DNS as your example.net DNS server. It will forward all requests for said domain.