ns4.gdnsdef.com has no CNAME records.
Question and response
Question
dig ns4.gdnsdef.com. NS
Answer
The response has no answer records.
Authority
gdnsdef.com. 9090 SOA ns3.gdnsdef.com. gdnssupport.nexusguard.com. 2015071601 10800 120 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0