AS10000 NCM Nagasaki Cable Media Inc.

NCM is Nagasaki Cable Media Inc., a community cable-television operator headquartered in Nagasaki City that sells cable TV, broadband internet, fixed-line phone and mobile service across Nagasaki, Saikai, Togitsu and Nagayo. AS10000 is the eyeball network behind that broadband product.

What it's used for

Residential and small-business cable broadband. The AS announces 20 IPv4 prefixes totalling roughly 73,700 addresses plus a single IPv6 /32, and the sampled reverse DNS is subscriber-pool naming throughout: hosts like cdu20m5.cncm.ne.jp and cmu07a5.cncm.ne.jp sit under NCM's own cncm.ne.jp service domain, with the cdu/cmu prefixes indexing cable-modem access concentrators rather than servers. Nothing in the sampled space looks like hosting or content infrastructure.

Notable

This is an eyeball network, and the routing shape says so plainly. Roughly 73,700 addresses against only 28 observed BGP neighbours is the classic access-ISP silhouette: a wholesale carrier with that much space would be peering with hundreds of ASes, whereas an access network buys transit from a couple of upstreams and peers locally. Geolocate this space to end users in western Kyushu, not to a datacentre.

Interesting

AS10000 is not carrying only NCM's own subscribers. Sampled PTRs include pl-126.52.0.5.cableone.ne.jp and pl-103.29.48.5.taku.ne.jp — CableOne (Takeo, Saga) and Taku Cable Media (Taku, Saga), two separate cable operators in the neighbouring prefecture. NCM is evidently acting as the shared ISP platform and BGP origin for smaller partner cable companies, which is a common arrangement among Japanese regional CATV operators and explains why the address space is spread across so many unrelated-looking blocks. The IP space is still eyeball space; the subscribers behind some of it just belong to a different cable company.