ns.ipn.de has no CNAME records.
Question and response
Question
dig ns.ipn.de. NS
Answer
The response has no answer records.
Authority
ipn.de. 10668 SOA ns.ipn.de. support.ipn-b.de. 2024091301 10800 3600 604800 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0