Reverse NS Lookup — Domains on Nameserver Infrastructure

Authoritative nameserver hostnames ultimately resolve to IP addresses operated by DNS hosting providers — Cloudflare DNS, Route53 nameserver pools, registrar branded NS clusters, or self-managed BIND servers. Domains using nameservers on shared infrastructure often share reverse-IP footprints on those addresses when providers consolidate DNS hosting nodes.

Our approach resolves the NS hostname you supply, then asks which domains reverse-IP databases associate with those addresses today. This approximates reverse nameserver research when full passive DNS NS indexes are unavailable in free tooling.

Enter bare hostnames without scheme — ns1.example.com not https URLs. nameserverIps lists IPv4 A records returned by public DNS. IPv6-only nameservers without A records produce empty IP lists and empty related domains with explanatory summary.

Glue records at parent zones are not required when public DNS resolves the NS hostname recursively from the internet.

Large providers assign multiple A records to nameserver hosts for redundancy. We query reverse-IP on up to three IPs to balance coverage against upstream rate limits, merging results into one deduplicated set.

Missing IPs in the sample may leave related domains undiscovered — rerun with sibling NS hostnames ns2, ns3 when infrastructure spans distinct hosts.

relatedDomains slices to one hundred entries for browser performance. domainCount reports full set size before display truncation. truncated true when more than one hundred exist — commercial investigations may need paid passive DNS for complete exports.

High counts often indicate shared registrar DNS infrastructure — thousands of unrelated customer domains expected, not necessarily affiliation between sites.

Commercial passive DNS indexes every observation of domains pointing at nameserver hostnames historically. Our note explicitly states limitation — we correlate via NS IP reverse-IP, which misses domains whose NS hostnames resolve to addresses without reverse-IP listing or use DNS anycast without shared reverse footprints.

Treat output as investigative lead generation, not court-ready exhaustive lists.

Phishing cluster analysts pivot from malicious domain NS records to related domains on same infrastructure. Brand protection teams map typosquat campaigns sharing registrar DNS pools. Academic researchers study DNS hosting concentration across the web.

Compare with reverse MX lookup when mail and DNS infrastructure split across providers.

Public DNS anycast returns different NS IP answers by resolver location — your lookup reflects one resolution path. Anycast reverse-IP may list domains unrelated to the nameserver's logical customer set when IP serves multiple anycast services.

Interpret high domain counts on major anycast DNS providers as infrastructure scale, not malicious clustering alone.

DNS compare tool contrasts NS records between two domains. IP history lookup shows domain migration timelines. PTR record lookup resolves individual NS IP reverse DNS hostnames for additional context.

Email-focused investigators cross-reference reverse MX lookup when NS and MX share provider infrastructure.

Reverse-IP upstreams throttle aggressive polling. Batch NS research should space queries — avoid hammering same registrar NS pool in tight loops.

We do not store your nameserver queries permanently — responsible use protects shared API quotas for all users.

Extended API action reverse-ns-lookup accepts host or query parameter with nameserver hostname. Parse nameserverIps, relatedDomains, domainCount, and truncated in JSON pipelines.

Automate deduplication client-side when merging results from ns1 through ns4 sequential queries.