AS10908 CLOUDFLOORAS

CLOUDFLOORAS-0 is CloudfloorDNS, a managed DNS provider. Its routing is unusually legible: this AS exists to carry authoritative nameservers, and almost nothing else.

What it's used for

DNS service. RIS shows 4 announced IPv4 prefixes totalling 1,024 addresses, 4 announced IPv6 prefixes (four /48s carved from 2620:1f::), and 1 observed neighbour.

The reverse DNS makes the purpose unambiguous. Every sampled address in every prefix resolves to a nameserver name, and the pattern is systematic: 199.73.82.x is ns1..cfdns.net, 199.73.83.x is ns2..cfdns.biz, 204.138.102.x is ns3..cfdns.info, and 192.188.176.x is ns4..cfdns.co.uk. One /24 per nameserver identity, and the last octet appears inside the hostname, so the whole block is generated as nameserver space rather than assigned host by host.

Spreading ns1 through ns4 across four different top-level domains, and four separate address blocks, is deliberate resilience engineering. A zone's delegation survives the loss of any one TLD's infrastructure, any one prefix, or any one registrar problem, which is precisely the failure mode a managed DNS provider is paid to avoid.

Notable

Judged by address count this is a tiny network, a thousand addresses. Judged by function it is the sort of network whose outage takes customer domains off the internet entirely, since a nameserver that cannot be reached is indistinguishable from a domain that does not exist.

Interesting

The clean one-block-per-nameserver layout is what lets DNS providers announce the same addresses from many locations at once. The size of the address space says nothing about the number of physical sites behind it.