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ASN lookup
Find the network behind an IP, or every prefix an AS number announces.
ASN data: IP Geolocation by DB-IP (CC BY 4.0).
An autonomous system (AS) is a network under one operator with its own routing policy: an internet provider, a cloud, a university, a large company. Each has a number (ASN) from a regional registry and announces blocks of IP addresses to the rest of the internet. AS1136 is KPN, AS15169 Google, AS16509 Amazon.
The lookup works both ways. Enter an IP address to find the network it belongs to, or an AS number to see its owner, how many addresses it announces, in which countries, and every prefix. The data covers about 82,000 autonomous systems and is refreshed monthly.
Common uses
- Blocking or allowing a whole network (a hosting provider, a cloud) at the firewall, using the downloaded prefix list.
- Telling residential visitors from datacenter traffic in your logs.
- Abuse reports: finding who operates the address that attacked you.
For the published ranges of the big clouds, see AWS, Google Cloud and Cloudflare; for everything registered in a country, the country IP ranges. Single addresses: IP lookup.