What is ASN
A unique ID for networks on the internet
Useful for routing analysis, ownership checks, and security triage
Quick summary
An Autonomous System Number (ASN) identifies a network or group of IP prefixes that share a routing policy on the internet. ISPs, cloud providers, and large organizations use ASNs to announce routes via BGP.
Key points
- Each ASN is a unique number, for example AS15169.
- One ASN can announce many IP prefixes.
- ASN ownership helps trace network responsibility.
Quick example
If an IP belongs to AS15169, it is part of Google's network. This helps you understand who owns the traffic path and where to escalate issues.
Common use cases
- Identify who owns or announces an IP range.
- Troubleshoot routing or peering issues.
- Track abuse sources during security reviews.
Where you see it
ASN data appears in IP geolocation results, BGP tools, and network reports. It is often shown as AS followed by a number (example: AS15169 for Google).
FAQ
Is an ASN the same as a domain owner?
No. An ASN represents a network operator, not necessarily the website owner.
Can one company have multiple ASNs?
Yes, large providers often operate multiple ASNs for different regions or services.
Does every IP belong to an ASN?
Public IPs do. Private or internal ranges are not routed on the public internet.