Apex domains cannot have CNAME records.
Question and response
Question
dig intgdc.com. NS
Answer
intgdc.com. 5 NS dns4.p07.nsone.net.
intgdc.com. 5 NS dns3.p07.nsone.net.
intgdc.com. 5 NS dns1.p07.nsone.net.
intgdc.com. 5 NS dns2.p07.nsone.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0