ASN Lookup
Who operates a network, when it was registered and everything it announces — from our copy of the global routing table.
Well-known networks
The internet is a network of networks. Each independently operated network — an ISP, a cloud provider, a university — is an autonomous system with a unique number (ASN) assigned by a regional internet registry. Autonomous systems exchange reachability using BGP: each one announces the IP prefixes it originates.
This page is built from our own copies of public data, refreshed every 24 hours: the AS name and every prefix it originates come from the global BGP table (APNIC), and the registration date and country from the delegation files of the five regional internet registries. A route that disappeared today may still be listed until the next refresh.
Frequently asked questions
How do I find the ASN of an IP address?
Look the address up in the IP lookup tool: the Network section shows the origin AS and the BGP prefix that covers it.
What is the difference between 16-bit and 32-bit ASNs?
Originally ASNs were 16-bit (up to 65535). RFC 6793 extended them to 32 bits; numbers above 65535 are now common for new networks.
Why does an AS announce no prefixes?
Many registered AS numbers are reserved for future use, used only for private peering, or belong to networks that have shut down. If it originates nothing in the global BGP table, it has no publicly routed addresses.