Autonomous system
AS4721 JCN JCOM Co., Ltd.
Residential ARIN
Summary
JCOM Co., Ltd. (former JCN)
isp legacy
JCN is one of the networks of JCOM Co., Ltd. (J:COM), Japan's largest cable television and cable-broadband operator. It carries the name of Japan Cablenet Limited (JCN), the operator J:COM absorbed in 2014.
What it's used for
- Consumer broadband and cable-TV subscriber access on the former JCN footprint, now operated as part of J:COM.
Notable
- This is eyeball address space: several hundred thousand IPv4 addresses handed out to residential cable-internet subscribers, so traffic to it is end users, not servers.
- J:COM took over JCN's shares from KDDI in December 2013 and completed the merger on 1 April 2014; the ASN and its address blocks survived the corporate consolidation under the old handle.
- J:COM runs more than one ASN — this one is specifically the ex-JCN network, not the group's primary AS.
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
Recorded at 2 exchanges in 1 country, largest first.
| Exchange | Location | Their address |
|---|---|---|
| JPIX Tokyo | Tokyo, Japan | 210.171.224.142 |
| Network Service Provider IXP (Distributed IX in Edo) | Tokyo, Japan | 202.249.2.168 |
Transit providers
1 upstream, 0 downstream and 2 adjacent networks observed; most-used upstreams first.
| AS | Network | Paths seen |
|---|---|---|
| AS9824 | JCOM Co., Ltd. | 9,564 |
Exchange presence is recorded rather than inferred: the directory collected by Packet Clearing House (https://www.pch.net/ixp/data) on 2026-10-11, licensed CC BY-NC-SA 3.0. Transit is inferred from observed BGP paths, never declared by either party.
Address space
Summary
IPv4 54 prefixes · 632K addresses IPv6 1 prefixes
| Country | Name | Prefixes |
|---|---|---|
| JP | Japan | 55 |
Registry
Allocation record
- Registry
- ARIN
- Handle
AS4721- Registry name
- JCN
- Registered
- 1995-08-30
- Last changed
- 2022-02-18
- Allocation
- allocated
Routing security
RPKI and IRR
- RPKI
- 100% valid · 163 valid, 0 with no ROA
- ROAs
- 57 authorising AS4721
- ASPA
- no ASPA record
- IRR
- 100% registered · 163 of 163 announcements
- Route objects
- 173 naming AS4721
Reputation
Classification and threat
Residential Fixed-line consumer ISP. Addresses here are homes.
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: 431 networks and 1,768 prefixes, as published 2026-10-12. 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