cns2.knownhost.com has no CNAME records.
Question and response
Question
dig cns2.knownhost.com. NS
Answer
The response has no answer records.
Authority
knownhost.com. 1612 SOA cns1.knownhost.com. dns.cloudflare.com. 2397101162 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0