The internet is a massive web of interconnected networks. At its foundation are Autonomous Systems (AS) — groups of IP routing prefixes managed by a single organization under one unified routing policy. Every AS gets a unique identifier called an Autonomous System Number (ASN), which plays a key role in the Border Gateway Protocol (BGP) for exchanging routing info between networks.
Today, over 120,000 ASNs are assigned worldwide, but only a select few have achieved truly iconic status. These stand out for their historical significance, enormous scale, critical infrastructure roles, or constant visibility in global routing tables. They form the internet’s backbone, serve billions daily, and represent key chapters in internet history.
Here are some of the most legendary ASNs, and why network engineers, researchers, and internet historians hold them in such high regard.
1. AS1 – LVLT-1 (Now Part of Lumen/Level 3)
AS1 is one of the very first public ASNs ever assigned. It dates back to the dawn of the commercial internet, when Level 3 Communications (now Lumen Technologies) built one of the original high-capacity fiber backbones.
In networking communities, ultra-low ASN numbers like AS1 are considered “prestigious” or “OG” — handed out in the internet’s early days (pre-1990s boom). Holding AS1 symbolically marks the very start of the ASN registry.
2. AS2 – UDEL-DCN (University of Delaware)
Another ultra-low ASN from the internet’s academic roots, AS2 was assigned to the University of Delaware. Early ASNs (roughly AS1–AS10) went mostly to universities, research labs, and pioneers involved in the transition from ARPANET to NSFNET.
AS2 is living history — a reminder of when the internet was mainly non-commercial, focused on education and research.
3. AS3 – MIT-GATEWAYS (Massachusetts Institute of Technology)
MIT received AS3, fitting the pattern of early ASNs going to elite research universities. Institutions like MIT, USC (AS4), Carnegie Mellon (AS9), and Rice (AS8) were crucial in developing core internet protocols and infrastructure.
These low numbers spark nostalgia for the internet’s origins in defense-funded research and academia.
4. AS3356 – Lumen Technologies (Formerly Level 3)
Frequently ranked as one of the largest and most connected ASNs globally — often #1 in customer cone size per CAIDA’s AS Rank. AS3356 is a true Tier-1 backbone provider with vast peering, huge IPv4/IPv6 announcements, and essential transit for massive global traffic volumes.
Its enormous reach means countless networks route through or peer with AS3356 for efficient global connectivity.
5. AS15169 – Google LLC
Google’s primary ASN is instantly familiar to anyone monitoring BGP or debugging connectivity issues. It originates a tremendous number of prefixes and powers services used by billions: Google Search, YouTube, Google Cloud, Android, and more.
AS15169 regularly tops lists for originated prefixes, global visibility, and even “risky” range associations (purely due to scale). It’s one of the most prominent ASNs in worldwide routing tables.
6. AS16509 – Amazon.com, Inc.
Amazon’s flagship ASN drives AWS (Amazon Web Services), the world’s leading cloud platform. It announces vast IPv4 space and underpins e-commerce, Prime Video streaming, cloud services, and thousands of third-party websites.
Like Google’s ASN, it’s legendary for sheer size — outages or BGP flaps here can ripple across huge swaths of the internet.
7. AS13335 – Cloudflare, Inc.
Cloudflare’s ASN has skyrocketed in fame thanks to its dominance as a CDN, DDoS protection service, public DNS resolver (1.1.1.1), and reverse proxy. It handles an enormous share of global web traffic.
It often leads rankings for announced prefixes or high-volume hosted content, and it’s celebrated for making the internet faster and safer for millions of websites.
Other Notable Mentions
- Early DoD-linked ASNs (e.g., in the AS749 range) for massive advertised address space.
- Historic Tier-1 providers like AS701 (Verizon), AS1299 (Arelion/Telia), and AS2914 (NTT) — pillars of the internet’s default-free zone backbone.
Why These ASNs Matter
These iconic ASNs aren’t famous just for size — they symbolize the internet’s evolution: from academic/research origins to today’s hyper-scale commercial giants. Low historic numbers carry prestige, while modern heavyweights like Google, Amazon, and Cloudflare show how a handful of organizations now support everyday online life.
For anyone serious about internet infrastructure, understanding these ASNs is essential. They explain global routing dynamics, peering disputes, route leaks, and why certain networks feel “closer” or more reliable than others.
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