How to query an ASN with whois

An ASN WHOIS lookup identifies the registry record for an autonomous system number before the number is used in an allowlist, abuse note, routing ticket, or ownership check. The record should show the assigned ASN, registry, organization, and reference details that tie the number to a responsible resource holder.

IANA can identify which regional internet registry is responsible for an ASN block. The detailed assignment record usually lives at ARIN, RIPE NCC, APNIC, LACNIC, or AFRINIC, so an explicit follow-up query prevents a referral record from being mistaken for the final resource record.

WHOIS records show number-resource registration, not full live routing. Use Team Cymru, route collectors, or ASN intelligence tools when the decision depends on originated prefixes, AS paths, or current route changes.

1. Normalize the ASN before querying.

   AS15169

   Keep the AS prefix for readability. If a registry rejects it, retry with the numeric value only.

2. Ask IANA which registry serves the ASN block.

   $ whois -h whois.iana.org AS15169
   % IANA WHOIS server
   % This query returned 1 object
   
   refer:        whois.arin.net
   as-block:     13312-15359
   organisation: Assigned by ARIN
   whois:        whois.arin.net

3. Query the referred registry for the ASN record.

   $ whois -h whois.arin.net AS15169
   ASNumber:       15169
   ASName:         GOOGLE
   ASHandle:       AS15169
   RegDate:        2000-03-30
   Updated:        2012-02-24
   Ref:            https://rdap.arin.net/registry/autnum/15169
   
   OrgName:        Google LLC
   OrgId:          GOGL
   ##### snipped #####

   Output fields differ by registry. For a registration check, look for the ASN object, registry reference, organization, status, and update date before using contact fields.

4. Save the registry record when the result supports a ticket or access decision.

   $ whois -h whois.arin.net AS15169 > AS15169.whois

   Related: How to save raw whois output

5. Verify that the referral and final record answer the registration question.

   IANA refer:  whois.arin.net
   IANA block:  13312-15359
   ARIN object: AS15169
   ARIN org:    Google LLC

   For registry responsibility, the referred registry WHOIS record is enough. For live routing, pair it with route collector, BGP, or ASN intelligence evidence.