AS9824 JTCL-JP-AS JCOM Co., Ltd.

AS9824 (JTCL-JP-AS) is held by JCOM Co., Ltd. — J:COM, Japan's largest cable multiple-system operator, headquartered in Tokyo and a KDDI/Sumitomo joint venture. The handle preserves the company's former name, Jupiter Telecommunications. This is the eyeball network behind J:COM's cable broadband service.

What it's used for

RIS sees 231 IPv4 prefixes carrying 4,745,216 addresses, plus 62 IPv6 prefixes, announced through only 31 BGP neighbours. Nearly 4.75 million addresses against a peer count in the low tens is the unmistakable signature of a residential access network: it consumes transit and peering to reach the internet on behalf of its own subscribers, and sells no meaningful wholesale service. The inventory is consistent with that — several /13s (42.144.0.0/13, 110.128.0.0/13, 27.136.0.0/13) and a long series of /16s, contiguous JPNIC space allocated to a national operator, not a patchwork of acquired blocks. Sampled reverse DNS is uniform and decisive: every address returns a generated NN-NN-NN-NN.rev.home.ne.jp PTR, home.ne.jp being J:COM's own subscriber domain.

Notable

• J:COM serves cable footprints across Sapporo, Sendai, the Kanto region, Kansai and Fukuoka, and sells TV, telephony, mobile and even electricity alongside broadband — but this AS carries the internet side.
• IPv6 is broadly deployed: 62 prefixes, including 2001:ff0:: and 2405:120x:: ranges, so subscribers are dual-stacked at scale.
• The uniform machine-generated rDNS across the whole footprint is what lets geolocation and abuse tooling recognise J:COM subscriber addresses on sight.