asn.dev

Autonomous system

AS33657 CMCS

Unclassified ARIN

IPv4 addresses 1.55M 179 prefixes
IPv6 prefixes 230 counted as prefixes, not addresses
Countries 1 mostly US
Exchanges 0 recorded by PCH
Upstreams 2 127 downstream
Flagged prefixes 0 none

Summary

Comcast

United States of America · AI-generated

residential cable isp us

The AS handle CMCS is held by Comcast Cable Communications, LLC.

What it's used for

  • The address space carries residential cable internet services, evidenced by reverse DNS entries like c-68-33-191-254.hsd1.va.comcast.net and c-76-100-64-0.hsd1.md.comcast.net.
  • The inventory includes 1,553,408 IPv4 addresses and 233 IPv6 prefixes, with 179 IPv4 prefixes in inventory.
  • With 133 observed neighbours, the high address-to-neighbour ratio indicates this is an access/eyeball network rather than a transit provider.

Notable

  • Registrants vary slightly across prefixes, including Comcast Cable Communications, LLC, Comcast Cable Communications, Inc., Comcast Cable Communications Holdings, Inc, and Comcast Cable Communications, IP Services, reflecting corporate restructuring or historical acquisitions.
  • The address inventory is finely subdivided into 179 IPv4 prefixes, consistent with a large-scale residential ISP managing distinct regional or service segments.

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, 127 downstream and 143 adjacent networks observed; most-used upstreams first.

ASNetworkPaths seen
AS7922Comcast Cable Communications, LLC9,104
AS3356Level 3 Parent, LLC100

Exchange presence is recorded rather than inferred: the directory collected by Packet Clearing House (https://www.pch.net/ixp/data) on 2026-10-16, 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 179 prefixes · 1.55M addresses IPv6 230 prefixes

CountryNamePrefixes
USUnited States of America409

Registry

Allocation record

ARIN · via Atlas (registry + RDAP)
Registry
ARIN
Handle
AS33657
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
97% valid · 262 valid, 5 with no ROA 2 RPKI-invalid
ROAs
702 authorising AS33657
ASPA
no ASPA record
IRR
0% registered · 0 of 269 announcements 5 other origin
Route objects
27 naming AS33657

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 1,783 prefixes, as published 2026-10-17. 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