dns1.nrtc.net has no NS records.
NS records for this zone are defined at nrtc.net.
NS records for this zone are defined at nrtc.net.
Question and response
Question
dig dns1.nrtc.net. NS
Answer
The response has no answer records.
Authority
nrtc.net. 300 SOA dns1.nrtc.net. root.dns1.nrtc.net. 3070753216 10800 3600 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0