ASN Lookup

An ASN identifies which network on the internet is responsible for a given block of IP addresses - this lookup finds that network's owner, its registry, and every address range it currently announces.

ASN (Autonomous System Number)

A unique number identifying one network on the internet - assigned to an ISP, a cloud provider, a university, or any organization big enough to run its own routing policy. It's what lets BGP, the internet's core routing protocol, know which network to hand traffic to.

Announced prefixes

The specific IP address blocks (in CIDR notation, e.g. 8.8.8.0/24) a network has told the rest of the internet it's responsible for. A large network can announce thousands of these across multiple countries.

Registry (RIR)

Which of the five regional internet registries - ARIN, RIPE, APNIC, LACNIC, AFRINIC - allocated this ASN or address block. That's the network's formal region of registration, not necessarily where its traffic actually flows.

Searching an IP instead of an ASN

Finds which network currently announces the specific block that address falls within - the same lookup a router itself effectively performs to find a route to it.

Have a single IP address instead of an ASN? See IP Lookup.