dns1.iplanisp.com has no CNAME records.
Question and response
Question
dig dns1.iplanisp.com. NS
Answer
The response has no answer records.
Authority
iplanisp.com. 100 SOA dns1.iplanisp.com.ar. hostmaster.iplan.com.ar. 2018122808 3600 600 1400000 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0