AS16503 ZAYO-16503

Four letters from a company that no longer exists name ten of the eleven blocks, and they name the reverse zone too.

What it's used for

• A carrier's network. Eleven IPv4 prefixes announced from the United States, no IPv6, twenty thousand two hundred and twenty-four addresses, through one observed BGP neighbour.

Notable

• Ten blocks carry the same four initials, in three variants: the bare letters, the letters with a two, and the letters with a three. Eight of the ten use the third variant.
• Those initials belong to an acquired business, not to the company in the registrant field, which is the same on every block.
• The eleventh block is named after a different acquisition entirely, a backbone brand that the carrier absorbed.
• Sixteen of eighteen queried addresses answered, every one with its address hyphenated, then two letters that are the first two of those same acquired initials, then a domain naming the carrier's enterprise arm.
• The AS handle is the carrier's brand with this network's own number appended, which is the only field that names the current owner without an acquisition attached.

Interesting

• Twenty thousand addresses behind a single observed neighbour is a carrier's edge network rather than its backbone. The routing here is a leaf, not a crossroads.
• The numbered variants are a record of buying the same company's space in instalments: the first block got the plain name, and each later batch got the next number. Nobody ever went back and renamed the first.