ns1.ci.nttsvc.com has no NS records.
NS records for this zone are defined at ci.nttsvc.com.
NS records for this zone are defined at ci.nttsvc.com.
Question and response
Question
dig ns1.ci.nttsvc.com. NS
Answer
The response has no answer records.
Authority
ci.nttsvc.com. 600 SOA ns0.ci.nttsvc.com. hostmaster.ci.nttsvc.com. 1773391241 16384 1800 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0