Curious Cloudflare DNS behavior

Havard Eidnes he at
Fri May 29 17:51:12 UTC 2020

> Again, twice in 6 weeks Cloudflare DNS seems to loose complete
> track of usbank dot com as a domain.

All the name servers for that domain are placed in that same
domain.  That in itself perhaps isn't a problem.  However, they
also all have IPv4 addresses (no IPv6 in sight) in the same /16
which is routed as a single entity in the global routing table.
Thus, if that network should fall off the net from Cloudflare's
(or any other recursive resolver operator's) perspective for some
reason or other, the names in that domain will all be
unresolveable, and a recursive resolver which is unable to reach
any of the publishing name servers will return SERVFAIL.


- Håvard

More information about the NANOG mailing list