[ Autonomous System Number | Network Owner | BGP Routing Info ]
Enter IP address or ASN (AS number)
What is ASN?
Autonomous System Number identifies networks on the internet.
Examples:
AS15169 = Google
AS13335 = Cloudflare
AS16509 = Amazon
Use cases:
Network analysis, ISP identification, routing diagnostics
What is an ASN? An Autonomous System Number (ASN) uniquely identifies a network on the internet. Each ISP, cloud provider, or large organization has one or more ASNs to control their IP address blocks and routing policies.
Why it matters: ASNs help with network troubleshooting, identifying service providers, understanding BGP routing, security analysis, and tracing network ownership.
Common ASNs: Google (AS15169), Cloudflare (AS13335), Amazon AWS (AS16509), Microsoft Azure (AS8075), Comcast (AS7922).
How ASNs Work: Think of ASNs as unique postal codes for the internet's routing system. Just as postal codes help mail reach the right destination, ASNs help data packets find their way through the global network. Each autonomous system is a collection of IP networks and routers under a single organization's control that presents a common routing policy to the internet.
ASN Types: There are two types of ASNs - 16-bit ASNs (ranging from 0 to 65535) and 32-bit ASNs (from 0 to 4,294,967,295). The original 16-bit ASN space was running out, so the 32-bit system was introduced. Public ASNs are globally unique and used for internet routing, while private ASNs (64512-65534 in 16-bit range) are used for internal networks.
Real-World Applications: Network engineers use ASN lookups to diagnose routing issues, trace DDoS attacks back to their source networks, verify CDN configurations, analyze peering relationships between networks, and identify the true hosting provider behind proxied services. Security teams rely on ASN data to block malicious traffic sources, whitelist trusted networks, and investigate suspicious connections.
BGP and ASNs: Border Gateway Protocol (BGP) is the routing protocol that uses ASNs to exchange routing information between autonomous systems. Each ASN announces which IP prefixes it can reach, creating a map of the entire internet's routing structure. Understanding ASN relationships helps explain why your data takes certain paths and can reveal network performance bottlenecks.
Related: IP Lookup · WHOIS · Traceroute
What is an ASN? An ASN (Autonomous System Number) is a unique ID for a network that announces IP routes via BGP (Border Gateway Protocol). It's assigned by regional internet registries (ARIN, RIPE, APNIC) and identifies organizations that manage substantial IP address blocks.
Can I lookup an ASN from an IP? Yes. Many IP intelligence providers map IPs to the organization and ASN that owns/announces the route. This tool automatically determines whether you're entering an IP address or ASN and performs the appropriate lookup. You can enter formats like "AS15169", "15169", or any IP address to find its associated ASN.
Does ASN tell me who exactly is using the IP? Not reliably. It identifies the network owner/route announcer, not a specific person. VPNs/proxies can also change what you see. For example, if someone uses AWS cloud services, you'll see Amazon's ASN, not the actual website owner. ASN data shows infrastructure ownership, not end-user identity.
What should I use ASN lookup for? Troubleshooting routing/latency, identifying datacenter traffic, and security investigations. Pair it with IP Lookup and WHOIS for more context. Network administrators use it to verify peering agreements, analyze traffic sources, configure firewall rules based on ASN, and track down abuse sources.
Why do some ASNs have multiple IP ranges? Large networks often control numerous IP blocks across different regions and services. For example, Google's AS15169 announces thousands of IP prefixes worldwide to serve traffic from geographically distributed data centers. Organizations acquire IP ranges over time through allocation requests, acquisitions, or mergers, all announced under their primary ASN.
How can I get my own ASN? To obtain an ASN, you must have a unique routing policy and be multihomed (connected to at least two different upstream providers) or provide transit for other networks. Apply through your regional internet registry (RIR) - ARIN for North America, RIPE NCC for Europe, APNIC for Asia-Pacific, LACNIC for Latin America, or AFRINIC for Africa. Requirements include demonstrating technical capability, paying annual fees ($500-$2000+), and maintaining proper IP address assignments.