pool.ukrtel.net has no CNAME records.
Question and response
Question
dig pool.ukrtel.net. NS
Answer
The response has no answer records.
Authority
ukrtel.net. 10396 SOA ns1-01.azure-dns.com. hostmaster.ukrtel.net. 2021100400 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0