nsa.ces.net has no NS records.
NS records for this zone are defined at ces.net.
NS records for this zone are defined at ces.net.
Question and response
Question
dig nsa.ces.net. NS
Answer
The response has no answer records.
Authority
ces.net. 900 SOA nsa.cesnet.cz. hostmaster.cesnet.cz. 2019072261 28800 7200 1209600 900
Additional
. 0 OPT ; payload 1472, xrcode 0, version 0, flags 0