auth-ns3.csail.mit.edu has no CNAME records.
Question and response
Question
dig auth-ns3.csail.mit.edu. NS
Answer
The response has no answer records.
Authority
csail.mit.edu. 900 SOA auth-ns0.csail.mit.edu. bug-domain.csail.mit.edu. 253603962 1800 300 604800 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0