An NS record names an authoritative server for a zone. The same record type
appears in parent referrals and in the child zone, but those copies have
different authority and operational roles.
Purpose and type code
IANA registers NS as type code 2
[1]. Its RDATA
is one domain name identifying a host that should be authoritative for the
named zone [3].
Presentation format
example.com. 86400 IN NS ns1.example.net.
example.com. 86400 IN NS ns2.example.net.Each target is a hostname, not an IP address. Address records for those hostnames are resolved separately.
Owner-name and coexistence rules
At a delegation, the parent zone publishes NS records for the child. The child normally publishes an authoritative NS RRset at its own apex. The sets should agree operationally, but changing only the child copy does not usually change the parent’s delegation. The DNS hierarchy delegates authority along zone boundaries [2].
An NS target must not be a CNAME alias [4]. When a target lies inside the delegated child, the referral needs address glue to avoid a circular dependency. Glue is A or AAAA data in the parent referral, not a separate record type; current glue requirements are specified by RFC 9471 [5].
Caching and changes
Delegation NS, child NS, and relevant address records can have different TTLs and cache lifetimes. A nameserver migration must keep old and new service available through the overlap instead of treating one control-panel update as instantaneous.
Security and operational limits
An NS answer names servers; it does not prove they answer authoritatively, serve the intended zone contents, agree with one another, or have reachable IPv4 and IPv6 paths. Parent access usually belongs to the registrant or registrar account, while child-zone NS data belongs to the DNS operator.
DNSSEC adds DS and signed child data to the change sequence. Incorrect DS data can make otherwise reachable answers fail validation.
Verify
Check the parent’s referral, each child’s authoritative NS RRset, nameserver addresses, and direct authoritative answers. Record which server and layer produced each result. Stop a change if the new servers disagree or are not authoritative.
Next step
Review zones, delegation, and glue for the full mental model, or continue to the SOA record reference.