ns3.fortinet.com has no NS records.
NS records for this zone are defined at fortinet.com.
NS records for this zone are defined at fortinet.com.
Question and response
Question
dig ns3.fortinet.com. NS
Answer
The response has no answer records.
Authority
fortinet.com. 300 SOA ns3.fortinet.com. mis.fortinet.com. 1 604800 7200 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0