ns1.softlayer.net has no CNAME records.
Question and response
Question
dig ns1.softlayer.net. NS
Answer
The response has no answer records.
Authority
softlayer.net. 5120 SOA ns1.softlayer.com. root.softlayer.com. 2024110700 7200 600 1728000 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0