Autonomous system detail

AS104

Announced

Operated by COLORADO-AS - University of Colorado at Boulder.

Summary

// analyst note
Active university network with ~2 peers and 2 upstreams; appears in traceroutes through Boulder. Legacy institutional, low risk. ARIN RDAP RegDate 1987-04-09 (Confirmed).
// security note
NEUTRAL/DATED: no notable public abuse signal found as of 2026-06-09; clean R&E network.
IPv4 prefixes
20
~91.1K addresses
IPv6 prefixes
1
announced
Peer networks
2
2 up · 0 down
IANA block
1-1876
Assigned by ARIN
[ 01 ] — Context

About this ASN.

Updated  ·  Confidence: High

AS104 is a legacy spring-1987 allocation registered under ARIN to the University of Colorado at Boulder (Information Technology Services, Boulder, CO; abuse contact abuse@colorado.edu), carrying the handle "COLORADO-AS." It is the campus AS for CU Boulder, announcing the legacy 128.138.0.0/16 Class B network among others (also 198.11.16.0/20 and 192.12.238.0/24), with roughly two peers and two upstreams and about 77 hosted domains across 36 IPs. This is a flagship research-university allocation from the original AS block and appears in traceroutes through Boulder. The ARIN RDAP RegDate is 1987-04-09 (Confirmed). For triage this is an active university network — a clean, low-risk legacy institutional allocation. No notable public abuse signal was found as of June 2026.

Operator
University of Colorado at Boulder (Information Technology Services, Boulder, CO) [Confirmed] — ARIN RDAP
Country / RIR
US, ARIN [Confirmed]
Allocated
ARIN RDAP RegDate 1987-04-09 [Confirmed] — ARIN RDAP
Org status
active

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-06-09; clean R&E network — ipinfo.io

Network & routing

Our research recorded 3 IPv4 prefixes; RIPEstat currently announces 20.
Network type
research / education (university) [Confirmed]
Size
includes 128.138.0.0/16, 198.11.16.0/20, 192.12.238.0/24; ~77 hosted domains across 36 IPs — IPinfo (2026-06)
Routing/peering
active; ~2 peers, ~2 upstreams; RPKI unknown — ipinfo.io
Notable usage
[current] The campus AS for the University of Colorado Boulder, announcing the legacy 128.138.0.0/16 Class B network; a flagship research-university allocation from the original AS block — colorado.edu
Related ASNs
none specifically confirmed for this profile
Analyst note
Active university network with ~2 peers and 2 upstreams; appears in traceroutes through Boulder. Legacy institutional, low risk.
[ 02 ] — Announced prefixes

What this network routes.

21 prefixes total · RIPEstat data · cached, not real-time
// IPv4 prefixes20
  1. 128.138.0.0/16/16
  2. 129.19.192.0/18/18
  3. 198.11.16.0/20/20
  4. 146.5.20.0/22/22
  5. 192.12.241.0/24/24
  6. 198.59.81.0/24/24
  7. 192.12.242.0/24/24
  8. 198.59.82.0/24/24
  9. 192.12.244.0/24/24
  10. 192.12.240.0/24/24
  11. 198.59.52.0/24/24
  12. 192.12.245.0/24/24
  13. 204.228.80.0/24/24
  14. 198.59.51.0/24/24
  15. 198.59.7.0/24/24
  16. 198.59.54.0/24/24
  17. 198.59.55.0/24/24
  18. 198.59.70.0/24/24
  19. 192.12.238.0/24/24
  20. 198.59.83.0/24/24
// IPv6 prefixes1
  1. 2620:18f::/32/32
[ 03 ] — Notable peers & upstreams

Who it talks to.

2 observed neighbours
// Notable connectionsTop 2 of 2
ASNOperatorRole
AS3356 LEVEL3 - Level 3 Parent, LLC upstream
AS14041 AS-FRGP - University Corporation for Atmospheric Research upstream
Neighbours observed via public BGP collectors; not a complete peering list.