Apex domains cannot have CNAME records.
Question and response
Question
dig firewall-lange-it.dns.army. NS
Answer
firewall-lange-it.dns.army. 5 NS ns3.dynv6.com.
firewall-lange-it.dns.army. 5 NS ns2.dynv6.com.
firewall-lange-it.dns.army. 5 NS ns1.dynv6.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0