ftp.simstats.sentris.net has no NS records.
NS records for this zone are defined at sentris.net.
NS records for this zone are defined at sentris.net.
Question and response
Question
dig ftp.simstats.sentris.net. NS
Answer
ftp.simstats.sentris.net. 86400 CNAME www.simstats.sentris.net.
Authority
simstats.sentris.net. 86400 SOA ns.wahju.com. hostmaster.simstats.sentris.net. 2000050215 86400 3600 864000 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0