ASN Lookup
Look up the autonomous system, ISP, and country for an IP address or AS number
Usage
• IP address: enter an IPv4 (1.1.1.1) or IPv6 address
• AS number: enter in the format AS13335 or 13335
• Shows the autonomous system, ISP, and geographic location
What ASN lookup is for
An ASN lookup queries the global routing and IP registry databases to find the Autonomous System Number associated with an IP address, along with the ASN's registered name, the ISP or organization that operates it, and the country. An Autonomous System is a collection of IP prefixes under a single routing policy, typically operated by an ISP, cloud provider, or large enterprise.
Common uses include identifying the network operator behind an IP address, confirming which carrier or cloud an IP belongs to, cross-referencing ASN data with BGP route lookups for path analysis, and investigating traffic sources in security incident response.
Frequently asked questions
What is an ASN?
An Autonomous System Number (ASN) is a globally unique identifier assigned to a network operator (ISP, cloud provider, university, etc.) by a Regional Internet Registry. It is used in the BGP routing protocol to identify which organization controls a set of IP prefixes.
How is ASN lookup different from IP geolocation?
IP geolocation maps an IP to a physical location (country, city). ASN lookup maps an IP to a network operator — who owns and routes that IP block, which is often more useful for understanding network topology.
Can I look up an ASN directly?
Yes. Enter the ASN in the format AS13335 or just 13335 and the lookup will return the registered name, country, and associated IP prefixes for that autonomous system.
Can ASN lookup list every IP range of a cloud provider?
ASN lookup can show prefixes available in the current source, but providers can hold multiple ASNs and collection can be incomplete. Consult the provider’s official published ranges when a complete service IP list is required.
References and result limitations
Online results reflect the queried source or probe state at that time. Record the target, time, nodes or data source, and parameters when citing them. A single result does not establish continuous availability everywhere.
These references explain protocol or format rules; they do not endorse results produced by this site.