oko.fei.tuke.sk has no CNAME records.
Question and response
Question
dig oko.fei.tuke.sk. NS
Answer
The response has no answer records.
Authority
fei.tuke.sk. 10800 SOA oko.fei.tuke.sk. hostmaster.oko.fei.tuke.sk. 2026022701 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0