server.nethouse.cz has no CNAME records.
Question and response
Question
dig server.nethouse.cz. NS
Answer
The response has no answer records.
Authority
nethouse.cz. 10493 SOA ns1.wia.cz. hostmaster.wia.cz. 2025102402 14400 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0