ns4.luadns.net has no NS records.
NS records for this zone are defined at luadns.net.
NS records for this zone are defined at luadns.net.
Question and response
Question
dig ns4.luadns.net. NS
Answer
The response has no answer records.
Authority
luadns.net. 3600 SOA ns1.luadns.net. hostmaster.luadns.com. 1772610617 1200 120 604800 3600
Additional
. 32768 OPT ; payload 512, xrcode 0, version 0, flags 32768