1.x7z.ru has no NS records.
NS records for this zone are defined at x7z.ru.
NS records for this zone are defined at x7z.ru.
Question and response
Question
dig 1.x7z.ru. NS
Answer
The response has no answer records.
Authority
x7z.ru. 300 SOA ns1.timeweb.ru. dns.timeweb.ru. 1042517 28800 7200 259200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0