asn.dev

Autonomous system

AS33667 CMCS

Unclassified ARIN

IPv4 addresses 999K 182 prefixes
IPv6 prefixes 133 counted as prefixes, not addresses
Countries 1 mostly US
Exchanges 0 recorded by PCH
Upstreams 2 142 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-67-181-127-255.hsd1.ca.comcast.net and netnames such as CENTRALCALI-CPE-17 and SACRAMENTO-9.
  • With 996,352 IPv4 addresses announced across 181 prefixes and 137 observed neighbours, the high address-to-neighbour ratio indicates a large-scale access network rather than a transit provider.

Notable

  • All sampled registrants align with the announcer, consistently listing Comcast Cable Communications, LLC or Comcast Cable Communications.
  • The inventory is finely subdivided into regional blocks, including specific Central California and Sacramento designations, 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, 142 downstream and 155 adjacent networks observed; most-used upstreams first.

ASNetworkPaths seen
AS7922Comcast Cable Communications, LLC2,839
AS3356Level 3 Parent, LLC1,024

Exchange presence is recorded rather than inferred: the directory collected by Packet Clearing House (https://www.pch.net/ixp/data) on 2026-10-14, 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 182 prefixes · 999K addresses IPv6 133 prefixes

CountryNamePrefixes
USUnited States of America315

Registry

Allocation record

ARIN · via Atlas (registry + RDAP)
Registry
ARIN
Handle
AS33667
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
88% valid · 101 valid, 12 with no ROA 2 RPKI-invalid
ROAs
486 authorising AS33667
ASPA
no ASPA record
IRR
61% registered · 70 of 115 announcements 16 other origin
Route objects
210 naming AS33667

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 1,771 prefixes, as published 2026-10-15. 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