IP Tools
ASN Lookup: Search Any Autonomous System Number
Every ISP, hosting provider, and large organization on the internet has an Autonomous System Number (ASN) that identifies their routing domain. Our ASN lookup tool provides detailed information about any ASN including the owning organization, registered IP prefixes, and peering relationships.
Launch in Mission ControlWhat It Measures
This tool returns the organization name, country, registered IP prefixes (IPv4 and IPv6 CIDR blocks), BGP routing details, and estimated number of IPs controlled by the ASN. It also shows upstream providers and peering relationships where available.
How It Works
- Queries WHOIS databases (ARIN, RIPE, APNIC, LACNIC, AFRINIC) for the ASN
- Retrieves BGP routing tables for announced prefixes
- Cross-references PeeringDB for peering and exchange information
- Returns comprehensive organization and routing data
Why It Matters
ASN information is fundamental to internet network analysis. Security teams use it to identify traffic sources, network engineers use it for routing decisions, and researchers use it to study internet topology. Knowing the ASN tells you exactly which company controls an IP range.
Understanding Your Results
There are no performance targets for ASN lookup as it is a reference tool rather than a measurement test. Valid results should include a registered organization name, at least one IP prefix, and a country of registration for any actively used ASN.
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Run ASN Lookup Now →Frequently Asked Questions
What is an Autonomous System (AS)?
An Autonomous System is a network or group of networks under a single administrative authority that uses a common routing policy. Each AS is identified by an ASN. ISPs, universities, cloud providers, and large corporations each manage their own AS and announce their IP ranges to the global BGP routing table.
How many ASNs are there?
As of 2024, there are over 100,000 active ASNs globally. The 16-bit ASN space (1 to 65535) is nearly exhausted, so 32-bit ASNs (up to 4 billion) are now being assigned. Large providers like Amazon, Google, and Comcast operate multiple ASNs for different regions and services.
Can I look up which ASN my connection uses?
Yes. Looking up your own public IP address reveals your ISP's ASN. This is useful for verifying that your traffic is routing through the expected provider and for understanding how your connection is identified to the global internet routing system.
What is BGP and how does it relate to ASNs?
BGP (Border Gateway Protocol) is the routing protocol that ASNs use to announce their IP prefixes and exchange routing information with each other. Each ASN announces which IP blocks it owns and which ASNs it can reach. BGP is the protocol that makes the global internet work as one interconnected network.
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