Networking Basics

What Is an ASN (Autonomous System Number)?

What Is an ASN

An Autonomous System Number (ASN) uniquely identifies an autonomous system (AS) on the Internet - typically a large ISP, cloud provider, or organization that manages its own network, such as China Telecom, Alibaba Cloud, or Google.

Why IP Lookups Show ASN

Every public IP belongs to an autonomous system. ASN databases tell you which organization manages an IP. For example:

What ASN Is Used For

ASNs are the foundation of Internet routing. ISPs exchange routes via BGP, which is organized by AS. For users, the ASN helps identify the true operator of an IP and distinguish datacenter IPs from residential broadband.

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Enter any IP to see its ASN and organization. →