_netblocks.ngenix.net has no CNAME records.
Question and response
Question
dig _netblocks.ngenix.net. NS
Answer
The response has no answer records.
Authority
ngenix.net. 300 SOA ns.ngenix.net. noc.ngenix.net. 1 7200 600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0