illustrious.xo.com has no NS records.
NS records for this zone are defined at xo.com.
NS records for this zone are defined at xo.com.
Question and response
Question
dig illustrious.xo.com. NS
Answer
The response has no answer records.
Authority
xo.com. 300 SOA ns-twbg.verizonwireless.com. hostmaster.xo.com. 2013072091 10800 3600 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0