Quick lookup: Find the ASN for any IP using the MyIPNow WHOIS Lookup.
What is an Autonomous System (ASN)?
An Autonomous System (AS) is a collection of IP networks under the control of a single organization that presents a common routing policy to the internet. Each AS is assigned a unique Autonomous System Number (ASN).
Key ASN concepts
Download CSV| Term | Description | Why it matters | Example |
|---|---|---|---|
| ASN | Unique identifier for an autonomous system | Routing identity | AS13335 |
| IP Prefixes | IP ranges announced by ASN | Traffic ownership | 104.16.0.0/12 |
| BGP | Routing protocol between ASNs | Path selection | AS_PATH |
| Upstream | Provider ASN | Internet connectivity | Tier-1 ISP |
| Downstream | Customer ASN | Traffic origin | Hosting provider |
| Peering | ASN-to-ASN exchange | Direct routing | IXP peering |
| RIR | ASN allocator | Governance | ARIN / RIPE |
| AS-SET | Group of ASNs | Routing policy | IRR objects |
How ASNs are used
- Routing traffic across the global internet
- Identifying IP ownership and responsibility
- Applying security and routing policies
ASN vs IP address vs ISP
- An IP address identifies a device or endpoint.
- An ASN identifies the network announcing IP ranges.
- An ISP is a business entity that may operate one or more ASNs.