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ASN Lookup - Autonomous System Intelligence
Explore any Autonomous System Number to understand network ownership, routing policies, peering relationships, and the IP prefixes announced by that network. ASN lookup provides essential context for network security and infrastructure analysis.
What Is an ASN?
An Autonomous System Number identifies a network or collection of networks under single administrative control. Every organization that participates in global internet routing - ISPs, cloud providers, enterprises, universities - operates one or more ASNs.
ASNs are the building blocks of internet routing. Understanding them reveals who controls network infrastructure and how traffic flows between providers.
ASN Lookup Results
Query any ASN to retrieve:
- Organization details - Company name, country, and registration date
- Announced prefixes - All IP address blocks the AS advertises via BGP
- Prefix count - Total IPv4 and IPv6 ranges controlled by the network
- Peering information - Upstream providers and peer relationships
- Routing policy - How the network connects to the global internet
Use Cases for ASN Analysis
Threat intelligence - Identify which network hosts malicious infrastructure. Some ASNs have reputations for hosting abuse; knowing the ASN behind an IP provides immediate context.
Network architecture - Understand how large organizations structure their networks. Major enterprises often operate multiple ASNs for different purposes or regions.
Peering decisions - Network operators use ASN data to evaluate potential peering partners and understand traffic paths.
IP attribution - When investigating an IP address, the ASN reveals the responsible organization more reliably than WHOIS data, which may show resellers or intermediaries.
Reading ASN Data
ASN numbers below 64511 are globally unique. Numbers 64512-65534 are reserved for private use. Four-byte ASNs (numbers above 65535) became necessary as the original two-byte space filled.
The prefixes announced by an ASN show its addressing footprint. A network announcing many small prefixes may be providing hosting services. One announcing a few large blocks is likely an ISP or enterprise.