Autonomous system
AS21508 COMCAST-21508
Unclassified DROP-listed space ARIN
Summary
Comcast
cable residential business isp
COMCAST-21508 is operated by Comcast Cable Communications, LLC.
What it's used for
- The address space carries residential and business cable internet services, evidenced by reverse DNS entries like
c-71-62-127-255.hsd1.va.comcast.netandc-50-189-239-254.unallocated.comcastbusiness.net. - With 689,152 IPv4 addresses announced against 47 observed neighbours, the high address-to-neighbour ratio indicates an access/eyeball network rather than a transit provider.
Notable
- Registrants are consistent with the announcer, including Comcast Cable Communications Holdings, Inc, Comcast Cable Communications, LLC, and Comcast Cable Communications, Inc.
- One prefix, 141.104.0.0/16, is registered to the Virginia Department of Education with netname
VAK12ED-NET, which does not fit the typical Comcast residential pattern. - The inventory includes 141 IPv4 prefixes and 71 IPv6 prefixes, with the largest blocks being /16s such as 71.62.0.0/16 and 174.179.0.0/16.
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
Internet exchanges
No exchange port on file. Many exchanges publish no participant list, so this is not proof of absence.
Transit providers
1 upstream, 49 downstream and 57 adjacent networks observed; most-used upstreams first.
| AS | Network | Paths seen |
|---|---|---|
| AS7922 | Comcast Cable Communications, LLC | 2,948 |
Exchange presence is recorded rather than inferred: the directory collected by Packet Clearing House (https://www.pch.net/ixp/data) on 2026-10-20, licensed CC BY-NC-SA 3.0. Transit is inferred from observed BGP paths, never declared by either party.
Address space
Summary
IPv4 142 prefixes · 689K addresses IPv6 71 prefixes
| Country | Name | Prefixes |
|---|---|---|
| US | United States of America | 213 |
Registry
Allocation record
- Registry
- ARIN
- Handle
AS21508- Registry name
- COMCAST-21508
- Registrant
- Comcast Cable Communications, LLC
- Abuse contact
- abuse@comcast.net
- Registered
- 2001-05-16
- Last changed
- 2021-01-25
- Allocation
- assigned
Routing security
RPKI and IRR
- RPKI
- 91% valid · 71 valid, 7 with no ROA
- ROAs
- 280 authorising AS21508
- ASPA
- no ASPA record
- IRR
- 3% registered · 2 of 78 announcements 5 other origin
- Route objects
- 27 naming AS21508
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.
1 DROP match Announced space overlapping the DROP prefix list.
| Announced | DROP entry | Record |
|---|---|---|
| 204.194.47.0/24 | 204.194.40.0/21 | SBL668426 |
Spamhaus DROP ("Don't Route Or Peer") lists space and networks run by, or hijacked for, spam and cybercrime operations: 442 networks and 1,778 prefixes, as published 2026-10-20. 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