ASN

Autonomous System Number — the identifier of a network that announces IP prefixes.

An ASN identifies an autonomous system: a network with a single routing policy that announces one or more IP prefixes to the global BGP table. Comcast is AS7922, Vultr is AS20473, Cloudflare is AS13335.

For an IP check the ASN is the most useful single signal: it tells you who announces the address and what kind of organisation that is — consumer ISP, hosting provider, CDN, enterprise.

Ownership (RDAP) and announcement (BGP) are different questions. For platform risk, the announcing ASN matters more.

Related: Residential IP · Native IP · Dual ISP · CGNAT · BGP · RPKI · Anycast · CDN edge

Check an IP · Methodology · What platforms check