AS4997 AFS-WEST

AS4997 is registered to Zayo Bandwidth, the Denver-based fibre and bandwidth-infrastructure carrier, under the ARIN handle AFS-WEST. The handle predates Zayo: it comes from American Fiber Systems, the metro-fibre operator Zayo acquired in 2010.

What it's used for

Zayo sells dark fibre, wavelengths, Ethernet transport, and IP transit to carriers, hyperscalers, data centres, and large enterprises. AS4997 is one of the secondary ASNs in that estate rather than the main backbone, which runs as [AS6461](https://asn.ipinfo.app/AS6461). The roughly 22,000 addresses under it are customer and infrastructure assignments carried over the Zayo network.

Notable

This is carrier and business address space, not an eyeball pool. Ranges here tend to land on enterprise sites, colocation cages, and network infrastructure, so they behave much more like commercial or hosting addresses than residential ones.

American Fiber Systems built metro fibre in mid-sized western and midwestern US markets, and the AFS-WEST naming reflects that regional split. When Zayo bought the company its number resources came along and the ARIN org record was updated while the original handle stayed.

Interesting

Zayo's registry footprint is a map of the 2000s and 2010s fibre roll-up: the company grew through a long series of acquisitions, and each one left behind ASNs, IP blocks, and handles named after operators that no longer exist. Reading Zayo's ARIN records is a decent way to reconstruct which regional fibre builders got consolidated.