mgo.OCS.RU has no CNAME records.
Question and response
Question
dig mgo.OCS.RU. NS
Answer
The response has no answer records.
Authority
ocs.ru. 3470 SOA ns.ocs.ru. admin.ocs.ru. 2026030501 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0