Check an Autonomous System Number (ASN) for IP prefixes (subnets) or lookup an IP address (IPv4 or IPv6) to get details of the AS.

To search all ASN's belonging to an organisation, simply enter a text search string.

Valid Input AS3333 Name (company name to search)

ASN Query Format

Perform ASN lookups as shown in the examples below. Enter either as a single query, a list (IP's or AS Numbers), or a comma-separated list.

Lookup one or more IP's

Single query or a list
Comma separated,

Lookup one or more AS Numbers

Single query or a list
Comma separated

Search for AS Names

Search single queries

What is an Autonomous System (AS)

The Internet is made up of Autonomous Systems, these are collections of IP routing prefixes that allow Internet connected systems to communicate with each other. Without this routing the Internet simply would not work.

Use this tool to identify the registered owner of an IP range, in that the system owner that contains the IP address. Keep in mind that there is no direct correlation between the IP address location from the ASN and geolocation. Many organisations have Autonomous Systems that span continents; if an IP address is found in an AS based in the United States, this does not necessarily mean the IP address is on a system physically located within the United States.

The ASN search tool found here is for quick lookups of an IP address or Autonomous System Number (ASN). Using the Free version of the tool has a limit of 50 lookups a day; this includes use of the other IP Tools that has made available.

IPv6 ASN Lookup

An ASN can be made up of IPv4 and IPv6 prefixes. Our tool will show all prefixes within the ASN including IPv6 network ranges. Querying an IPv6 address with the tool will show the ASN that the address belongs to.

When using the ASN search to query a list of IP addresses you are able to mix IPv4 and IPv6 addresses within the one query.

ASN Bulk Lookup

Non-members can use the form above to enter up to 25 IP addresses or AS numbers to query. Results can be exported to XLSX for inclusion in your security reports or other tools.

ASN Lookup Limits

FREE USER Membership
Queries / day 50 500 - 20000
# based on plan
Max Query Size 25 20000

With a membership query up to 20000 IP addresses at once. A gold mine of data for security analysts, network defenders and other cyber security professionals.

To use the API see the details below, the API is only configured for single queries.

ASN Lookup API

This tool is built on a simple API that we have provided to the public as a Free service. To use the FREE version simply query the API and get your results. If you wish to use more than the 50 queries per day quota Remove limits with a Full Membership..

Using the ASN API is a simple matter of querying the following URL with an IP address, or ASN, appended to the "q" parameter. See below for an example. You can put this URL into a browser, use curl, or a scripting language such as php, python, or ruby to make the HTTP request. If you are looking up an ASN ensure the format is as shown in the second example.


Checking a List

Using the API querying the AS of a list of IP address is easily achieved with simple scripting.

while read line; do
done < ipaddress-list.txt

IP Tags / Blocklists

We have recently implemented additional IP address meta data from a well known public and open source security lists. If the IP address queried is listed in these resources it will be tagged in the table.
List Name Description Link
DShield A database of IP addresses reported for suspicious activities maintained by the well known SANS Institute.
AlienVault OTX An open threat exchange platform providing access to a global community-driven threat data. Alienvault
Cisco Talos Offers advanced threat intelligence and protection against Internet security risks. Cisco Talso (Feodo) Tracks and monitors Feodo Trojan botnet activities and malware.
Spamhaus (Drop / eDrop) Maintains lists of IPs from which unsolicited bulk emails are received. Spamhaus
Firehol (level 3) A blocklist aggregating various feeds to protect against the most severe attacks. Firehol 3
Tor Network Provides information on Tor nodes, focusing on anonymity and privacy online. Tor Project

Other BGP Resources

If you require more detail regarding the BGP routing of an Autonomous System, the Shadow Server Project has an excellent query tool available using DNS or Whois. There is also a Python module available for querying the service.

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Use Cases

Website Recon?

Fingerprint Web App
Technologies in Bulk

Whatweb / Wappalyzer

Remove limits with a full membership

More info available