ns17.knipp.net has no CNAME records.
Question and response
Question
dig ns17.knipp.net. NS
Answer
The response has no answer records.
Authority
knipp.net. 10800 SOA ns2.knipp.de. dnsmaster.irondns.net. 2021042160 10800 3000 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0