Apex domains cannot have CNAME records.
Question and response
Question
dig ispnet.net. NS
Answer
ispnet.net. 5 NS queens1.tinkelman.com.
ispnet.net. 5 NS ns4.ispnet.net.
ispnet.net. 5 NS ns1.ispnet.net.
ispnet.net. 5 NS ns2.ispnet.net.
ispnet.net. 5 NS ns3.ispnet.net.
Authority
The response has no authority records.
Additional
ns1.ispnet.net. 5 A 199.224.0.146
ns2.ispnet.net. 5 A 199.224.0.154
ns3.ispnet.net. 5 A 204.141.40.135
ns4.ispnet.net. 5 A 100.8.228.75
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0