dns3.rackhosting.com has no CNAME records.
Question and response
Question
dig dns3.rackhosting.com. NS
Answer
The response has no answer records.
Authority
rackhosting.com. 578 SOA dns1.rackhosting.com. drift.rackhosting.com. 1770905515 10800 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0