ns01.ilmserver.de has no CNAME records.
Question and response
Question
dig ns01.ilmserver.de. NS
Answer
The response has no answer records.
Authority
ilmserver.de. 5459 SOA ns01.ilmserver.de. info.ilm-provider.de. 2022022100 43200 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0