AS15404 COLT Technology Services Group

The netnames read as a customer list: a hospital trust, a patent office, a mobile operator, a manufacturer.

What it's used for

• A business carrier operating across the continent. One hundred and twenty-six IPv4 prefixes and ten IPv6 prefixes announced from the United Kingdom, one hundred and forty-two thousand addresses.

Notable

• Almost none of the netnames name the carrier. They name the organisations whose space it carries: a hospital trust with a netname of forty-two characters, a national patent office on two blocks, a mobile operator on two more, a components manufacturer, and four blocks under one four letter code.
• Several of those customer netnames carry their own country codes and allocation dates, from jurisdictions other than the one the routes are announced from.
• The largest single announcement is a /16, sixty-five thousand addresses in one route.
• Eighteen addresses were queried for reverse DNS and none returned a name.

Interesting

• This is what a business carrier's routing table looks like from outside: a directory of who buys connectivity from it. Each netname is a customer relationship recorded in a public database.
• The hospital trust's block is the one worth pausing on. A /16 of health service address space reaching the internet through a commercial carrier is an ordinary arrangement with an unusual concentration of sensitive traffic behind it.
• Nothing answering in reverse across a network this large is the carrier's choice, and it means the customer names in the registry are the only labels available.