To add — You can do delegated zones by specifying NS records for a subdomain within the parent zone. If you’re talking about NS for a second level domain (“exa

To add — You can do delegated zones by specifying NS records for a subdomain within the parent zone. If you’re talking about NS for a second level domain (“example” in example.com) you would want glue records which are essentially a “lookaside” to prevent circular dependencies. Glue records are really just A records with clout, returned with the IP of your name server. This glue is maintained by the higher level authoritative zone. So you query for example.org and the nameserver for .org returns ns1.example.org as the name server for your zone, as well as the IP address for that server. This is why you could run a DNS server at ns1.example.org as your authoritative DNS.