ns.kellerbu.de has no CNAME records.
Question and response
Question
dig ns.kellerbu.de. NS
Answer
The response has no answer records.
Authority
kellerbu.de. 33 SOA ns.checkdomain.de. hostmaster.checkdomain.de. 2023071701 40000 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0