unknown.telstraglobal.net has no CNAME records.
Question and response
Question
dig unknown.telstraglobal.net. NS
Answer
The response has no answer records.
Authority
telstraglobal.net. 10800 SOA ns03.telstraglobal.net. ipnoc.telstraglobal.net. 2026022001 3600 3600 3600000 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0