AS12676 NCORE-AS HKN GmbH

A German carrier with 125 neighbours, four other companies' address blocks, and IPv6 prefixes cut on boundaries that reverse DNS cannot follow.

What it's used for

• Access and transit in Germany. 74,496 addresses in eleven IPv4 prefixes, six IPv6 prefixes, and 125 observed BGP neighbours.

Notable

• Netnames trace the company's own allocations: DE-NCORE-990827, DE-NCORE-991123, DE-NCORE-20051207 on three separate blocks, and DE-NCORE-20150309.
• Four blocks belong to other organisations: dng IT GmbH, ibeco-Systems GmbH, cojama Infosystems GmbH, and one named ANTISPAMEUROPE-NET.
• The IPv6 announcements include a /39 and two /34s: 2a02:4c00::/39, 2a02:4c07:4000::/34 and 2a02:4c07:8000::/34.
• Two sampled addresses answered, as dynamic-0-4-205-88.b2bdsl.de and dynamic-255-7-205-88.b2bdsl.de.

Interesting

• Those /34 and /39 boundaries do not land on a multiple of four bits, and reverse DNS for IPv6 is delegated one hexadecimal digit at a time. A prefix that ends mid-digit cannot be handed to a customer as a single reverse zone; it has to be delegated as several, or not at all. Choosing such a size buys precise address accounting and pays for it in every reverse lookup afterwards.
• The hostnames read dynamic on a product named b2bdsl, business DSL. The two ideas sit badly together: a business line usually implies a fixed address, and the template says otherwise. Both sampled names are the first and last address of their subnets, so the naming is generated across the whole range regardless of which addresses a customer can use.
• Announcing four other companies' registrations alongside its own is what distinguishes a carrier from a hosting provider. The customers keep their registry identity; only the routing is bought.