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ASN lookup

The network behind an AS number: who runs it, where it's registered and how to reach its abuse desk.

With or without the AS, like AS13335 or 13335.

More options

Include the raw RDAP JSON from the Regional Internet Registry in the result. Large; off by default.

Try:

Results for AS64512

Checked live lookup2 ms

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Reserved

A reserved address or name

This is a special-purpose value, so no public registry holds a record for it.

  • AS64512 is a special-purpose AS number: Private Use (RFC 6996).
Structured result (JSON) · 955 B
{
  "query": {
    "kind": "autnum",
    "key": "64512",
    "display": "AS64512",
    "input": "AS64512",
    "autnum": {
      "asn": 64512,
      "special": {
        "kind": "private-asn",
        "name": "Private Use",
        "range": "64512-65534",
        "rfc": "RFC 6996"
      }
    },
    "notices": [
      {
        "code": "SPECIAL_PURPOSE",
        "message": "AS64512 is a special-purpose AS number: Private Use (RFC 6996).",
        "data": {
          "kind": "private-asn",
          "range": "64512-65534",
          "rfc": "RFC 6996"
        }
      }
    ]
  },
  "status": "special_purpose",
  "source": "none",
  "provenance": {
    "trace": [
      {
        "step": "input",
        "label": "Special-purpose range: Private Use (RFC 6996)",
        "status": "SPECIAL_PURPOSE",
        "ms": 0,
        "note": "64512-65534"
      }
    ],
    "totalMs": 0,
    "fetchedAt": "2026-11-14T17:44:50.099Z",
    "cache": "miss"
  }
}

What an ASN is and what you get

An autonomous system (AS) is a network, or a group of networks, run by one organisation under a single routing policy. Its AS number, or ASN, is the ID it uses to announce its IP address blocks to the rest of the internet over BGP, the protocol networks use to tell each other which addresses they can reach. Google uses AS15169, Cloudflare AS13335 and Amazon AS16509, and thousands of ISPs, universities and companies have their own.

This lookup returns the registration record for a number: who holds it, the name they gave it, the country, which of the five regional internet registries (RIRs) handed it out, when it was registered and last changed, and the abuse contact when one is published. It is the paper record. It does not say which address blocks the network announces today.

How to use it

  1. Enter the numberAccepted forms are AS13335, as 13335, ASN13335 and plain 13335. Asdot, the high.low form some routers and logs use, works too: 6.6784 is 6 * 65536 + 6784, which is AS400000.
  2. Read the holder and the abuse contactThe holder is the organisation the registry holds responsible for the AS. The abuse contact is the right place to report attacks that come from its networks. Not every record publishes one, and the result says so when it does not.
  3. Start from an IP address insteadRun the address through the IP WHOIS lookup to see who it is registered to. When the registry names an origin AS there, it links back to this page.

Reading the result

  • Holder. The organisation the registry says is responsible. It can be a parent company or a hosting provider rather than the brand you know.
  • Name. A short label on the record, such as GOOGLE or CLOUDFLARENET. Some registries put an ID there instead, like ORG-SL75-AFRINIC. The registry's own ID for the record, the handle, is in the JSON.
  • Country. The country on the record, or the one in the holder's postal address if the record has none. It says where the holder is based, not where its routers are.
  • Registry. Which of ARIN, RIPE NCC, APNIC, LACNIC or AFRINIC manages the number. A few records are answered by a national registry, such as Brazil's registro.br, and the Registry field reads Unknown for those.
  • Dates. When the registry recorded the number and when it last changed.
  • A block, not one number. Some numbers sit inside a range the registry gave to one organisation. AS8075 is part of AS8068 to AS8075, which belongs to Microsoft, and the result names that block.

Some numbers are reserved and have no public holder. LookupOwl explains them instead of failing, and asks no registry about them:

ASN rangeMeaningDefined in
0Reserved. Not a real network; used to say an address block must not be routedRFC 7607
23456AS_TRANS: a stand-in for 32-bit ASNs in old softwareRFC 6793
64496 to 64511 and 65536 to 65551Documentation and examplesRFC 5398
64512 to 65534 and 4200000000 to 4294967294Private useRFC 6996
65535 and 4294967295ReservedRFC 7300
65552 to 131071Reserved by IANA, not yet assignedIANA AS numbers registry

Common problems

  • Not allocated. A number that IANA has not yet handed to any registry, such as AS250000, is reported as not allocated.
  • No record. The number falls in a registry's range, but the registry has no record of it. Check for a typo first.
  • Private or reserved number. Private numbers turn up inside company networks and with providers that strip them from routes. They have no public record. The table above lists them.
  • The holder is not the website owner. Networks are often run by a subsidiary, a hosting company or a managed-service provider.
  • The registry did not answer. You will see a retry message, or a recent stored copy that is labelled as one. Wait a minute and try again.

How the lookup works

The number is turned into a plain integer and checked against the reserved list above first, so special numbers are answered without any request. For the rest, LookupOwl finds the registry in IANA's AS number bootstrap file and asks that registry's RDAP server (RDAP is the modern, JSON replacement for WHOIS) for /autnum/<number>. It follows any redirect, for example from LACNIC to a national registry, and shows the autnum object that comes back. Recent answers are kept briefly so repeat lookups are quick.

Shell
# Same data from a terminal
curl -sL https://rdap.org/autnum/13335 | jq '{handle, name, startAutnum, endAutnum}'

# Classic WHOIS
whois AS13335

Standards

  • RFC 4271: BGP-4, where AS numbers are used for routing.
  • RFC 6793: 4-byte AS numbers. RFC 5396: the asplain, asdot and asdot+ ways of writing them.
  • RFC 5398, RFC 6996, RFC 7300, RFC 7607: documentation, private and reserved AS numbers.
  • RFC 9082, RFC 9083 and RFC 9224: the RDAP /autnum/ query, the autnum object it returns and the IANA bootstrap file that says which registry to ask.

Questions people ask

What does ASN stand for?

ASN stands for autonomous system number. It names a whole network, so it is not an IP address and does not point at one machine. One ASN usually covers many address blocks. IANA gives each registry ranges of numbers, and the registry hands them to the organisations it serves.

How do I find the ASN of an IP address?

Ask a BGP service, because the AS that announces an address is routing data, not registration data. Sites such as bgp.tools, bgp.he.net and RIPEstat show it. The IP WHOIS lookup here lists origin AS numbers only when the registry publishes them, which few do, so a missing one is normal. Once you have the number, paste it above to see who holds it.

Can an organisation have more than one ASN?

Yes. Large companies often run several, for example one per region or one inherited from an acquired business, and some networks use separate ASNs for transit and for customers. Each number has its own record, so look each one up to see which holder and abuse contact it points to.

Who should I contact about abuse from an AS?

Use the abuse contact on the AS record. If the trouble comes from one address, the abuse contact on that address's network, which the IP WHOIS lookup shows, is usually the better target. Send the date, the time zone and a few log lines, and skip large attachments. Some records publish no abuse contact, and the result says so.

What is a 4-byte ASN?

A 4-byte ASN is a 32-bit AS number. The original 16-bit numbers stopped at 65535 and began to run short, so RFC 6793 extended the range to 4,294,967,295. Numbers above 65535 are sometimes written in asdot as two parts, high then low, so 2.0 is AS131072. This tool accepts both spellings.

Do you show prefixes, peers and RPKI status?

No, this page shows the registry record only. Prefixes (the address blocks a network announces), upstream providers, peers and RPKI status (whether the address holder has approved an announcement) change often and come from BGP route collectors. For those, use a looking glass (a public view into a router's routing table) or a service such as bgp.he.net, bgp.tools or RIPEstat.

Can I look up an ASN from a script or an AI assistant?

Yes. The asn_lookup tool is on the free REST API and the MCP server, with no key. It returns the same record as structured data, and the raw RDAP JSON if you ask for it, but no prefixes or peers. See LookupOwl with AI agents.

Use it from AI, the API or the command line

Every LookupOwl tool is also a free API and an MCP tool, with no key and no account. This one is asn_lookup. Please be kind to the rate limits.

curl
curl "https://lookupowl.com/api/v1/tools/asn-lookup?q=AS13335"
MCP
claude mcp add --transport http lookupowl https://lookupowl.com/mcp

Description for AI agents · OpenAPI · llms.txt