ns2.nameserver.sk has no NS records.
NS records for this zone are defined at nameserver.sk.
NS records for this zone are defined at nameserver.sk.
Question and response
Question
dig ns2.nameserver.sk. NS
Answer
The response has no answer records.
Authority
nameserver.sk. 300 SOA ns1.dnsbackup.net. root.dnsbackup.net. 2026030401 36000 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0