NS record lookup

What the NS record lookup shows

An NS record lookup lists the nameservers a domain is served from, as the zone publishes them, each with its TTL. The query goes to Cloudflare's 1.1.1.1 from the IPVIEW server over the toolkit's own DNS engine. A single label such as ir is accepted, so the nameservers of a top-level zone can be asked for directly.

Nameservers are recorded in two places and this tool reads one. The zone's own NS records are what a resolver returns once it has found the zone; the parent's copy, held by the registry, is what sends the resolver there in the first place. After a transfer the two can disagree for days without an obvious symptom. The Delegation check asks the parent directly and compares.

How to read the result

The table lists Name, Value and TTL, one row per nameserver. Two or more on different networks is the usual expectation; a zone with one nameserver has one point of failure. Each nameserver is a name that must itself resolve; the Delegation check and the Full report resolve them and list the addresses. The TTL here is the time left on 1.1.1.1's cached copy and can be lower than the TTL set in the zone; the Full report asks the zone's own nameservers for that.

An empty answer is read from the response code. No NS record for a subdomain means it is not a zone of its own, which is normal; the records live in the parent. The name does not exist at all means NXDOMAIN. The query failed says the resolver got no answer, which is not a statement about the domain. A long TTL on NS records is sensible, since nameservers change rarely, but it also means a change is not seen everywhere for that long.

When it is useful

After changing hosting providers, to see whether the published nameservers are the new ones. If this tool shows the new set but the site still resolves to the old addresses, the parent may still point at the old nameservers; the Delegation check shows what the registry says.

When a domain resolves intermittently, one dead or lame nameserver in the list is a usual cause. The Full report asks the first six nameservers directly for the zone's SOA serial, lists those that did not answer and flags serials that disagree; the .txt report shows each nameserver's serial. WHOIS shows the nameservers as the registry has them, which for .ir domains is the only field IRNIC publishes.

Common questions

What is an NS record?

The record naming the servers authoritative for a zone, the ones that hold its records. A resolver follows NS records from the root down before it can answer any other question about the zone.

Why do the nameservers here differ from what my registrar shows?

This tool shows the zone's own NS records; the registrar holds the parent's copy. After a change they disagree until both are updated, and the Delegation check says which side is behind.

How long does a nameserver change take?

Up to the TTL of the old NS records at the parent, typically up to two days, plus the TTL shown here for resolvers that already know the zone. Keep the old nameservers serving until then.