Autonomous Systems: The Secret Map of the Internet

When you look up an IP address, you'll often see something like AS15169. This is an Autonomous System Number (ASN).

What is an Autonomous System (AS)?

An AS is a collection of IP prefixes under the control of a single entity (like Google or an ISP) that presents a common routing policy to the world.

The BGP Connection

While IP addresses tell you where a computer is, the ASN tells you which company is responsible for it. These ASNs use BGP to communicate routes to one another.

Check the ASN details of any IP with our ASN Lookup Tool.