Typically, the DNS domains that ADNR manages are subdomains of an existing DNS domain. For resolvers to reliably find resource records in the ADNR-managed subdomains, the ADNR-managed subdomain must be delegated by its parent domain. This enables resolvers to find resource records in the ADNR-managed subdomain if those resolvers are not pointing directly to the ADNR-managed name server. DNS queries from resolvers can follow the DNS delegation tree downward from the root domain, if necessary, and find an authoritative name server for the ADNR-managed subdomain.
Delegating a subdomain from a parent involves updating the parent domain's zone data file. In the parent's zone data file, an NS record and an associated A or AAAA glue record is added to represent each authoritative name server for the child domain. For example, to delegate the ADNR-managed mvsplex.mycorp.com zone from the mycorp.com zone, the following resource records are added to the zone data file for the mycorp.com zone:
mvsplex 86400 IN NS mvsnameserver.mvsplex.mycorp.com.
86400 IN NS networknameserver.mvsplex.mycorp.com.
mvsnameserver.mvsplex.mycorp.com. 86400 IN A 10.5.1.1
networknameserver.mvsplex.mycorp.com. 86400 IN AAAA 2001:0DB8:0:0:8:800:200C:417A
The example resource records delegate the mvsplex.mycorp.com zone to two authoritative name servers, one of which must be the master name server and the other a secondary name server.