When selecting the DNS of this system in the system parameters, the registration is unsuccessful and the DNS of the registrar can be selected.

DNS in system parameters

DNS server 1, 2: Must be such an address

Moreover, this address must be a domain name registered in the "Register DNS Server" in the domain name management.

Oh, understand. There is no problem with the same two, right?

Some registrars do not allow the same domain name

So is it OK to use a server?

This address must be a domain name registered in the "Register DNS Server" in the registrar. If he can register two DNS servers with the same IP, it will generally be fine.