dns1.rackhosting.com has no CNAME records.
Question and response
Question
dig dns1.rackhosting.com. NS
Answer
The response has no answer records.
Authority
rackhosting.com. 415 SOA dns1.rackhosting.com. drift.rackhosting.com. 1773059682 10800 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0