nb.GBlNET.net has no CNAME records.
Question and response
Question
dig nb.GBlNET.net. NS
Answer
The response has no answer records.
Authority
GBlNET.net. 10741 SOA ns.GBlNET.net. vvv.GBlNET.net. 2026022701 10800 1200 1209600 259200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0