dns1.cv.net has no CNAME records.
Question and response
Question
dig dns1.cv.net. NS
Answer
The response has no answer records.
Authority
cv.net. 3600 SOA authns1.cv.net. abuse.optimum.net. 2013420129 7200 600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0