linuxhost.iassys.com has no NS records.
NS records for this zone are defined at iassys.com.
NS records for this zone are defined at iassys.com.
Question and response
Question
dig linuxhost.iassys.com. NS
Answer
The response has no answer records.
Authority
iassys.com. 3600 SOA DNS101.REGISTER.com. root.REGISTER.com. 125080511 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0