chat.ex-sis.ru has no CNAME records.
Question and response
Question
dig chat.ex-sis.ru. NS
Answer
The response has no answer records.
Authority
ex-sis.ru. 1274 SOA ns.ex-sis.ru. admin.pledpodushkin.ru. 44 10800 3600 604800 604800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0