lab5.totbb.net has no CNAME records.
Question and response
Question
dig lab5.totbb.net. NS
Answer
The response has no answer records.
Authority
totbb.net. 5116 SOA ns1.totbb.net. root.totbb.net. 2026012201 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0