AS10003 OCT-NET Ogaki Cable Television Co.,Inc.

OCT-NET is Ogaki Cable Television Co., Inc. (OCT), the community cable operator for Ogaki City in Gifu Prefecture. It sells cable TV, FTTH and cable broadband, and IP telephony to households in its franchise area, and AS10003 is the access network behind the internet product.

What it's used for

Residential and small-business broadband. The AS announces 13 IPv4 prefixes totalling roughly 45,000 addresses plus a single IPv6 /32. Every sampled address resolves under the operator's own service zone with an unmistakable subscriber-pool pattern: d175158112005.cable.ogaki-tv.ne.jp, d219117016005.cable.ogaki-tv.ne.jp — a d prefix, the zero-padded address encoded into the label, all sitting beneath a cable. subdomain. That naming exists to give customer-premises equipment a PTR at scale; it is not what server, backbone or management space looks like.

Notable

This is an eyeball network. About 45,000 addresses against 11 observed BGP neighbours is the classic access-ISP silhouette — a handful of upstreams and local peering, versus the hundreds of adjacencies a wholesale carrier of that size would carry. Geolocate the space to subscribers in western Gifu, not to a datacentre.

Interesting

The announced blocks are scattered across ranges from several different registries, which is unusual for a single-city Japanese CATV operator and looks at first glance like the address-broker shape. It probably is not: the prefixes carry first-party reverse DNS in OCT's own zone, which is the discriminator that separates a real operator with untidy, incrementally-acquired space from a broker announcing other people's blocks. Worth one caution, though — one sampled PTR encodes an address that does not match the host it answers for, so individual addresses here should not be geolocated on the strength of the hostname alone.