How to make a separate dns response for the host on which the dns server is running?

Question

Domain Name System

Keenetic Ultra II, Padavan firmware, dns - dnsmasq
Local owncloud server
Not at home, clients access server.ddnsname.org, to which the router responds, forwards the necessary ports to the OC server address, everything is fine. It is necessary that when the client is in LAN, the router would kick on request immediately to the IP address of the OC server. So everything is clear, you can directly through the hosts of the router, BUT:
it is necessary that the router itself, when requesting the server.ddnsname.org address, go to external dns servers and receive an external ip address. For what: the provider issues either gray or white ip-addresses (I didn’t understand, maybe only white ones, but from some there is no answer from outside), the router pings itself by the crown on the domain name, if there is no answer - reconnect, until then until I get a working ip address. And I'm tired of driving local traffic at home through the router's nat. Google did not give a clear answer, or I still did not understand what to tweak (dns horizon split, groups via dhcp-host and dhcp-option, etc.)

Answer 1

That's right - you need a split view DNS. It is configured (at least in bind'e) quite simply.
https://kb.isc.org/docs/aa-00851#

Answer 2

It's not very clear why the router needs to ping something to determine the IP, if it already knows perfectly well what address it was given :-) It's easier to register everything in HOSTS, and analyze the address on the external interface with a script. If there is gray, then reconnect until it becomes white.
But if gray addresses really began to appear there, get ready for the fact that soon they will all become gray. Most likely, the provider decided to monetize white IPs, i.e. soon they will be issued only upon direct requests and for money.