@KreatifMaksimum

You can overlay DigitalOceans’ DNS, though the IP addresses may change in the future so you’d be responsible for keeping up with that. You can run:

ping -c1 ns1.digitalocean.com

ping -c1 ns2.digitalocean.com

ping -c1 ns3.digitalocean.com

To get the current IP’s and use those to register new name servers with your registrar. How depends on your registrar as they all seem to do things a little differently.

The best way would be to run your own DNS servers, as then you’re in control of the name servers, though you’re also tasks with setting them up and managing them. I’d recommend taking a look at PowerDNS. There’s a few general purpose guides here:

https://www.digitalocean.com/community/tutorial_series/how-to-configure-dns-servers-with-powerdns-on-ubuntu-14-04

Although written for Ubuntu 14.04, they should work on 16.04/16.10 as well.

Ok, I have already did it but not work. My issue is different. For example;

Main Domain:
abcd.com

Clients’ Domains:
1234.com
5678.com
qxyz.com

I want to redirect clients’ domains to my ns1.abcd.com and ns2.abcd.com… But nameservers not found.