1. Connectivity
At least two authoritative nameservers are required. They must be reachable via IPv4. IPv6 reachability is mandatory for all new delegations as of 2026.
2. Protocol Support
Nameservers must fully comply with RFC 1034 and RFC 1035. Support for TCP queries (RFC 7766) is required.
3. Recursive Separation
It is strongly recommended, though not strictly enforced for small zones, that authoritative nameservers do not perform recursion.
4. Glue Records
Glue records are required only when the nameserver hostname is within the domain being delegated.