asn.dev

Autonomous system

AS33651 CMCS

Unclassified ARIN

IPv4 addresses 2.27M 190 prefixes
IPv6 prefixes 173 counted as prefixes, not addresses
Countries 1 mostly US
Exchanges 0 recorded by PCH
Upstreams 2 140 downstream
Flagged prefixes 0 none

Summary

Comcast

United States of America · AI-generated

residential cable isp us

CMCS is the AS handle for Comcast Cable Communications, LLC.

What it's used for

  • The address space carries residential cable internet services, evidenced by reverse DNS entries like c-24-4-128-0.hsd1.ca.comcast.net and netnames such as BAYAREA-CPE-23 and SFBA-CPE-49.
  • With 2,268,160 IPv4 addresses announced across 189 prefixes and 143 observed neighbours, the high address-to-neighbour ratio indicates a large access/eyeball network rather than a transit provider.

Notable

  • Registrants consistently identify as Comcast Cable Communications, LLC or its subsidiaries (e.g., Comcast Cable Communications, Inc., Comcast Cable Communications Holdings, Inc), aligning with the announcer.
  • The address inventory is finely subdivided into regional blocks, with netnames referencing specific markets like BAYAREA and SFBA, reflecting site-by-site segmentation of the corporate estate.

This description is AI-generated, best-effort context — not authoritative, and provided without any guarantee of accuracy. Source, and how to suggest an edit.

Interconnection

Peering at a glance

Full topology · Graph

Internet exchanges

No exchange port on file. Many exchanges publish no participant list, so this is not proof of absence.

Transit providers

2 upstream, 140 downstream and 155 adjacent networks observed; most-used upstreams first.

ASNetworkPaths seen
AS7922Comcast Cable Communications, LLC10,207
AS3356Level 3 Parent, LLC314

Exchange presence is recorded rather than inferred: the directory collected by Packet Clearing House (https://www.pch.net/ixp/data) on 2026-10-13, licensed CC BY-NC-SA 3.0. Transit is inferred from observed BGP paths, never declared by either party.

Address space

Summary

Shape and geography

IPv4 190 prefixes · 2.27M addresses IPv6 173 prefixes

CountryNamePrefixes
USUnited States of America363

Registry

Allocation record

ARIN · via Atlas (registry + RDAP)
Registry
ARIN
Handle
AS33651
Registry name
CMCS
Registrant
Comcast Cable Communications, LLC
Abuse contact
abuse@comcast.net
Registered
2005-02-16
Last changed
2021-01-25
Allocation
assigned

Routing security

RPKI and IRR

Full detail
RPKI
94% valid · 281 valid, 10 with no ROA 7 RPKI-invalid
ROAs
4,889 authorising AS33651
ASPA
no ASPA record
IRR
14% registered · 42 of 298 announcements 52 other origin
Route objects
103 naming AS33651

Reputation

Classification and threat

Unclassified Not in the curated lists. Most of the ~80,000 allocated ASNs are not.

Spamhaus DROP

Not on ASN-DROP The network as a whole is not listed.

No DROP prefixes None of its announced space is on the DROP prefix list.

Spamhaus DROP ("Don't Route Or Peer") lists space and networks run by, or hijacked for, spam and cybercrime operations: 442 networks and 1,773 prefixes, as published 2026-10-13. A short, high-confidence list, so a match is worth taking seriously, and absence from it says little on its own.

FBI IC3

No IC3 indicators Nothing from the FBI IC3 feed.

IC3 threat data is alpha. Absence of an indicator is not evidence of good behaviour, only of absence from this one feed.

Elsewhere

Cross-check