auth1.opendns.com has no CNAME records.
Question and response
Question
dig auth1.opendns.com. NS
Answer
The response has no answer records.
Authority
opendns.com. 768 SOA auth1.opendns.com. noc.opendns.com. 1771979084 16384 2048 1048576 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0