What is an NS record?

Short answer

An NS (Name Server) record states by which name servers a zone is served as authoritative (RFC 1035). NS records written to the parent zone delegate the child zone to these servers (delegation): e.g. when the name servers of TR7 GTM are shown at the registrar for example.com, the queries of this domain come to TR7. In TR7 GTM, NS is selected from the Record Type list and entered into the Record cell as a full name ending with a dot; if the dot is missing, the "Must end with dot(.)" warning is given (record type specific fields). The only record added automatically when a domain is created is the SOA record; the NS records of the zone are added separately.

Where It Is Used in TR7

Where	Field / label	What for
GTM → GTM Services → service name → Records → Add	Record Type = NS; Record cell	Stating the name servers of the zone or of a subdomain
Same screen, SOA record	SOA MNAME (default ns1.<domain>.) (record type specific fields)	The name of the zone's primary name server; kept consistent with one of the names in the NS records
Load Balancer → Profiles → Health Checks (DNS)	DNS Record Type = NS	Checking the DNS server with an NS query

• Each name in the NS record (e.g. ns1.example.com.) must resolve to the IP address of that name server; for the name that points to TR7, this address is the Frontend IP address on which the DNS service listens, and the A or AAAA record of that name is added to the same zone. If the name is inside its own zone, this address is also entered at the registrar as a glue record.
• A zone being defined in GTM is not enough on its own; without the parent zone NS records at the registrar pointing to TR7, queries do not reach TR7.

Common Misconceptions

• "Adding the NS record to GTM moves the domain to GTM." Delegation is done in the parent zone, at the registrar where the domain is registered; the NS records in GTM are a statement within the zone itself.
• "An NS record takes an IP address." NS points to a name; the address of the name server is given with an A or AAAA record.
• "A single name server is enough." So that answers can still be given when one server is unreachable, the zone is published with at least two name servers (RFC 1034); the second server can get the zone from TR7 with zone transfer (What are master and slave DNS servers?).

How it is done in the documentation

• Records · The Record Type Specific Fields
• Service Management · Frontend IPs
• GTM · Terminology

Related questions

• What is a DNS zone; how does it relate to a domain and a DNS record?
• What is an SOA record; what do its fields mean?
• What is a DS record; why is it submitted to the registrar in DNSSEC?