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NS Lookup

An NS lookup lists the name servers delegated for a domain.

This check runs on our server. The address you enter is used only for this check and is not stored.
Updated

This check runs on our server. The address you enter is used only for this check and is not stored.

How to use the NS Lookup

  1. Enter the domain.
  2. Choose a resolver. Authoritative mode asks those name servers after it has found them.
  3. Tick the robot check and press Look up.
  4. Each row is one name server hostname.

How it works

This check runs on our server. The domain is used for the query only.

NS records are the delegation: they name the hosts that hold the zone. A public resolver returns the set it has cached. Asking the authoritative servers returns the set in the zone. If those two lists differ, a delegation change is still moving through caches. The SOA page shows the serial that goes with the zone those servers hold.

Examples

  • Two NS hosts, ns1 and ns2, mean either one can answer for the zone.
  • A TTL of 86400 is one day. Parent zones often use a long TTL on the delegation.
  • No NS records, or NXDOMAIN, means the name is not a delegated zone from the resolver you asked.

Limitations

  • The page lists hostnames. It does not open a zone transfer.
  • Glue addresses (the A records of the name servers, stored at the parent) are not a separate column. Look those hosts up on the A page.
  • A stealth name server that is not in the NS set will not appear.

Frequently asked questions

What is an NS record?

It names a server that is authoritative for the zone. Resolvers use that list to find who can answer other queries for the domain.

How many name servers should a zone have?

At least two, on separate networks, so one outage does not take the domain's DNS with it. The lookup shows however many are published.

Why would the parent and the zone disagree?

The registrar publishes the delegation, and the zone publishes its own NS set. After a name-server change, those two lists can differ until both are updated.

Often used together with the NS Lookup.

  • SOA Record Lookup

    SOA fields for a zone, with the serial read as a date when it uses YYYYMMDDnn.

  • DNS Lookup

    One table of A, AAAA, MX, NS, TXT, SOA, and CAA records for a domain.