cust.dynamic.leunet.ch has no CNAME records.
Question and response
Question
dig cust.dynamic.leunet.ch. NS
Answer
The response has no answer records.
Authority
leunet.ch. 300 SOA ns1.leunet.ch. hostmaster.leunet.ch. 2020083136 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0