ns1.f5clouddns.com has no CNAME records.
Question and response
Question
dig ns1.f5clouddns.com. NS
Answer
The response has no answer records.
Authority
f5clouddns.COM. 1511 SOA ns1.f5clouddns.COM. f5xc-dns.f5.COM. 2023012606 86400 7200 604800 1900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0