b.icann-servers.net has no CNAME records.
Question and response
Question
dig b.icann-servers.net. NS
Answer
The response has no answer records.
Authority
icann-servers.net. 3317 SOA sns.dns.icann.org. noc.dns.icann.org. 2022121925 7200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0