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Autonomous System (ASN) Lookup

Inspect network owners, BGP peering paths, RIR allocations, and announced CIDR prefixes.

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Major Backbone & Cloud Autonomous Systems

ASNOrganizationCountryAnnounced PrefixesRole
AS15169Google LLCUS3,200+Content / Cloud
AS13335Cloudflare, Inc.US2,800+CDN / Anycast
AS16509Amazon AWSUS5,100+Cloud Infrastructure
AS8075Microsoft CorporationUS4,400+Enterprise Cloud
AS32934Meta PlatformsUS1,900+Social / Content
AS20940Akamai TechnologiesNL1,400+Global CDN
AS3356Lumen (Level 3)US22,000+Tier 1 Transit
AS1299Arelion (Telia)SE18,000+Tier 1 Transit

How Autonomous Systems Route Global Internet Traffic

The internet is not a single monolith. It is a cooperative mesh of over 100,000 distinct networks called Autonomous Systems.

Each AS operates Border Gateway Protocol (BGP) routers that announce reachability to its IP address prefixes. These networks connect either via Peering (settlement-free exchange of mutual traffic at Internet Exchange Points like DE-CIX, AMS-IX, or Equinix) or IP Transit (commercial contracts where a customer AS pays a transit provider for global upstream connectivity).

Frequently Asked Questions

What is an Autonomous System Number (ASN)?▼

An Autonomous System Number (ASN) is a globally unique identifier allocated by IANA through Regional Internet Registries (RIRs). It identifies a connected group of IP networks operating under a single technical administrative and routing policy using Border Gateway Protocol (BGP).

What is the difference between a 16-bit and 32-bit ASN?▼

Historically, ASNs were 16-bit integers (ranging from 1 to 65,535). As internet connectivity expanded, RFC 4893 introduced 32-bit ASNs (ranging up to 4,294,967,295), expanding the address space to over 4 billion autonomous routing entities.

What is a Tier 1 Transit Provider?▼

A Tier 1 network (such as Lumen AS3356, Arelion AS1299, or NTT AS2914) can reach every other network on the global internet solely via settlement-free peering relationships without paying for commercial IP transit.

How do ASNs relate to IP addresses?▼

An IP address does not route itself. An Autonomous System announces IP prefixes (CIDR blocks) to adjacent networks using BGP. When you send a packet to an IP address, global routers examine BGP routing tables to send the traffic to the corresponding ASN.