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Autonomous System Lookup (AS / ASN / IP)

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


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.

Using this tool you are able to quickly identify the owner of an IP range, in that the system owner that contains the IP address. It is worth noting that there is no direct correlation between and IP address ASN and a geolocation. Many organisations have Autonomous Systems that span continents so if you find an IP address in an AS based in the United States that does not necessarily mean the IP address is on a system physically located within the United States.

The ASN search tool I have built here is for ad-hoc lookups of an IP address or Autonomous System Number (ASN). Using the Free version of this tool has a limit of 100 lookups a day, this includes use of the other IP Tools that HackerTarget.com has made available.

ASN Lookup API

This tool is built on an simple API that we have provided to the public. No signup or keys are required, simply query the API and get your results. If you wish to use more than the 100 queries per day quota, additional lookups are available with all of our membership plans.

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 could 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.

curl https://api.hackertarget.com/aslookup/?q=1.1.1.1
curl https://api.hackertarget.com/aslookup/?q=AS15169

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
curl https://api.hackertarget.com/aslookup/?q=$line
done < ipaddress-list.txt

Alternatively you can try the ASN lookup on our Traceroute Project page.

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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