Apex domains cannot have CNAME records.
Question and response
Question
dig msdp1.com. NS
Answer
msdp1.com. 5 NS ns3.msdp1.com.
msdp1.com. 5 NS ns1.msdp1.com.
msdp1.com. 5 NS ns2.msdp1.com.
msdp1.com. 5 NS ns4.msdp1.com.
Authority
The response has no authority records.
Additional
ns1.msdp1.com. 5 A 205.251.194.41
ns2.msdp1.com. 5 A 205.251.199.89
ns3.msdp1.com. 5 A 205.251.197.77
ns4.msdp1.com. 5 A 205.251.192.48
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0