nsgslb1.rt.ru has no CNAME records.
Question and response
Question
dig nsgslb1.rt.ru. NS
Answer
The response has no answer records.
Authority
rt.ru. 600 SOA ns1.rostelecom.ru. hostmaster.rt.ru. 2026030602 600 7200 1209600 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0