ns.corpnet.cz has no CNAME records.
Question and response
Question
dig ns.corpnet.cz. NS
Answer
The response has no answer records.
Authority
corpnet.cz. 3600 SOA ns.corpnet.cz. root.ns.corpnet.cz. 2026022401 7200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0