f.qtlcdncn.info has no NS records.
NS records for this zone are defined at qtlcdncn.info.
NS records for this zone are defined at qtlcdncn.info.
Question and response
Question
dig f.qtlcdncn.info. NS
Answer
The response has no answer records.
Authority
qtlcdncn.info. 300 SOA g.qtlcdncn.info. webmaster.qtlcdncn.info. 1591778141 7200 3600 64800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0