AS3

AS3 is a legacy single-digit allocation registered under ARIN to the Massachusetts Institute of Technology, and it remains a busy production network. It originates roughly 100 IPv4 prefixes and 13 IPv6 prefixes (~1.84 million IPv4 addresses), including ranges derived from MIT's iconic legacy 18.0.0.0/8 block (such as 18.0.0.0/11), and hosts domains including w3.org and debian.org. A notable history point: MIT sold the upper half of its Net 18 — the 18.128.0.0/9 block, about 8 million addresses — to Amazon/AWS in 2017, while retaining AS3 and the 18.0.0.0/9 lower half. For triage this is a large, clean academic network encountered constantly in academic and open-source-mirror traffic; 18.x originations from AS3 are expected, while 18.128.0.0/9 should now cross-check to AWS. ARIN exposes no real ASN registration date for AS3 (the RegDate field shows a 1970-01-01 epoch placeholder), so the original assignment date is recorded as unknown. RPKI coverage is weak (zero valid, three invalid, remainder unknown), which is a hygiene note rather than abuse. No notable public abuse signal was found as of June 2026.

Operator

Massachusetts Institute of Technology (ARIN OrgId MIT-2, Cambridge, MA) [Confirmed] — ARIN RDAP

Country / RIR

US, ARIN [Confirmed]

Allocated

ARIN exposes no real ASN RegDate (1970-01-01 epoch placeholder; Updated 2010-09-27); original assignment Unknown

Org status

active — mit.edu

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-06-07; large clean academic network — bgp.he.net

Network & routing

Network type

research / education [Confirmed]

Size

~100 IPv4 prefixes, 13 IPv6 (~1.84M IPv4 addrs); incl. ranges from legacy 18.0.0.0/8 — bgp.he.net / bgp.tools (2026-06)

Routing/peering

1 IX; ~18 peers, ~14 upstreams; actively announcing; RPKI valid 0, invalid 3, remainder unknown — bgp.he.net, bgp.tools

Notable usage

[current] production MIT ASN; hosts w3.org, debian.org; originates legacy Net 18 ranges. [historical/dated] MIT sold 18.128.0.0/9 (~8M addrs) to Amazon/AWS in 2017, retaining AS3 and 18.0.0.0/9 — internetsociety.org, toonk.io

Related ASNs

AS396527 (Massachusetts Institute of Technology, small ASN) [Likely sibling]

Analyst note

A major, actively-routed university ASN holding historically iconic address space (old Net 18); treat 18.x originations from AS3 as expected, and cross-check 18.128.0.0/9 against AWS (post-2017 sale).