dns2.ubunet.es has no CNAME records.
Question and response
Question
dig dns2.ubunet.es. NS
Answer
The response has no answer records.
Authority
ubunet.es. 17 SOA dns19.ovh.net. tech.ovh.net. 2026021900 86400 3600 3600000 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0